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COVID-19 vaccines: Canadian Immunization Guide

For health professionals

Last partial content update: September 27, 2024

This chapter was updated based on the following guidance from the National Advisory Committee on Immunization (NACI):

This information is captured in the table of updates.

On this page

Key information (refer to text and tables for details)

What

Who

It is recommended that beginning in fall 2024, previously vaccinated and unvaccinated individuals at increased risk of SARS-CoV-2 infection or severe COVID-19 disease should be vaccinated with a JN.1 or KP.2 COVID-19 vaccine as follows:

All individuals 6 months of age and over not listed above may receive an updated vaccine (JN.1 or KP.2) beginning in the fall of 2024 (see Recommendations for use section).

How

Why

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Epidemiology

Disease description

Infectious agent

COVID-19 is caused by the SARS-CoV-2 virus, which was first recognized in Wuhan, China in December 2019.

Transmission

Current evidence suggests that SARS-CoV-2 is spread through the air by infectious respiratory particles created when an infected person breathes, coughs, sneezes, sings, shouts, or talks. A person may be infectious for up to 2 to 3 days before showing symptoms and most people are considered no longer infectious 10 days from onset of symptoms (or first detection of infection if asymptomatic), although some may be infectious for longer.

Variants of concern

Genetic mutations in the SARS-CoV-2 virus have led to the designation of variants of concern (VOCs). Such mutations may lead to changes in transmissibility, severity of disease or the level of protection offered by vaccines or previous infection. Since late December 2021, Omicron has been the predominantly circulating VOC with a variety of sub-lineages emerging.

More information on the VOCs reported in Canada is available in the COVID-19 epidemiology update. The COVID-19 Weekly Epidemiological Update by the World Health Organization (WHO) provides a summary on the global distribution and emerging evidence on VOC and variants of interest (VOI). Differences between VOC and VOI are available from SARS-CoV-2 variants: National definitions, classifications and public health actions.

Risk factors

Anyone can be infected with SARS-CoV-2. However, some populations are at increased risk of exposure to the virus (e.g., due to living or occupational settings), and some populations are at increased risk of severe disease and outcomes (e.g., hospitalization and death) due to biological factors (e.g., advanced age, pre-existing medical conditions, pregnancy) and social factors (e.g., socioeconomic status, belonging to a racialized population). Risks for exposure and risk factors for severe disease may overlap, further increasing overall risk. Any combination of these factors, as well as varying access to health care services, has the potential for disproportionate consequences for specific populations characterized by increased rates of infection and disease, severe illness, hospitalizations, and/or deaths.

There is a spectrum of COVID-19 disease severity, ranging from asymptomatic to mild, moderate, severe and fatal disease. Severe disease more often occurs in those with increasing age and those with underlying medical conditions, with the risk increasing with the number of underlying conditions. A list of underlying medical conditions associated with more severe COVID-19 disease can be found in COVID-19 signs, symptoms and severity of disease: A clinician guide.

There is limited evidence on clinical risk factors for severe COVID-19 disease in pediatric populations. Children at increased risk for severe outcomes may include children who are medically fragile/have medical complexities, children with more than one comorbidity, children with neurological disorders, children with chronic lung disease, and children with Down syndrome (Trisomy 21) and other immunocompromising conditions.

Spectrum of clinical illness and disease characteristics

The median incubation period (the time from exposure to symptom onset) for non-variant SARS-CoV-2 was estimated to be 4 to 7 days. For Omicron, the median incubation period is 2 to 4 days. The incubation period can range from 2 to 14 days.

Clinical presentation and symptoms of COVID-19 vary in frequency and severity, from asymptomatic to severe and fatal disease. To date, there is no list of symptoms that has been validated to have high specificity or sensitivity for COVID-19.

More information on the spectrum of clinical illness is available on the PHAC webpage for COVID-19 signs, symptoms and severity of disease: A clinician guide.

While most children and adolescents with COVID-19 have mild or no symptoms, some do experience severe disease. However, children and adolescents report fewer severe outcomes of COVID-19 (i.e., hospitalizations due to COVID-19, intensive care unit [ICU] admission, and deaths) compared to older age groups.

Children, adolescents and adults with SARS-CoV-2 infection are at risk of multisystem inflammatory syndrome (MIS), a rare but serious condition that can occur several weeks following SARS-CoV-2 infection. People infected with SARS-CoV-2 are also at risk of post COVID-19 condition (PCC), a condition in which symptoms persist for more than 8 weeks and are present 12 or more weeks following acute infection with SARS-CoV-2. Refer to Effectiveness of vaccination against post-COVID-19 condition.

Disease incidence

Global

Updated international data on COVID-19 cases and deaths are available.

Weekly epidemiological updates highlighting key global, regional and country-level data on COVID-19 cases and deaths are available from the WHO.

National

Updated national, provincial and territorial-level data on COVID-19 cases and deaths in Canada over time are available from the PHAC webpage on COVID-19 epidemiology update: Summary.

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Preparations authorized for use in Canada

Older versions of the COVID-19 vaccine are no longer authorized for use and no longer available. There are some preparations of COVID-19 vaccines that are authorized for use in Canada but are not available for specific age groups or whose availability is uncertain at the time of updating this chapter. All authorized COVID-19 vaccines are listed in the chapter Contents of immunizing agents authorized for use in Canada.

mRNA vaccines

COVID-19 vaccines that use mRNA platforms contain mRNA with modified nucleosides that code for the SARS-CoV-2 spike protein. The mRNA can encode for the spike protein from the original SARS-CoV-2 virus or from a VOC. The currently recommended mRNA vaccines code for the Omicron KP.2 sub-lineage. A lipid nanoparticle formulation delivers the mRNA into the recipient's cells. Once inside the cytoplasm of a cell, the mRNA provides instructions to the cell's protein production machinery to produce the trans-membrane spike protein antigen that becomes anchored on the cell's external surface. The mRNA does not enter the nucleus of the cell and does not interact with, or alter, human DNA. The immune system is engaged by both the transmembrane spike protein and immune receptors carrying spike antigens to induce humoral and cellular immune responses. The mRNA, lipid nanoparticle, and spike protein are degraded or excreted within days to weeks from time of immunization. mRNA vaccines are not live vaccines and cannot cause infection in the host.

Protein subunit vaccine

The protein subunit vaccine consists of a purified full-length SARS-CoV-2 recombinant spike protein of JN.1 nanoparticle co-formulated with the adjuvant Matrix-M. Matrix-M is a novel saponin-based adjuvant that facilitates activation of the cells of the innate immune system, which enhances the magnitude of the spike protein-specific immune response.

Viral vector (non-replicating) vaccines

Two (2) viral vector vaccines had been authorized for use in Canada for adults 18 years of age and older: Vaxzevria™ (ChAdOx1-S recombinant) from AstraZeneca Canada (along with the version manufactured by the Serum Institute of India and marketed briefly in Canada as COVISHIELD) and Jcovden COVID-19 vaccine (Ad26.COV2.S) from Janssen Inc. They are no longer authorized or available in Canada.

Anti-SARS-CoV-2 monoclonal antibodies authorized for pre-exposure prophylaxis of COVID-19

EVUSHELD™ (a combination of two recombinant human monoclonal antibodies, Tixagevimab and cilgavimab) was previously authorized for use for the prevention of COVID-19 and for treatment of mild to moderate COVID-19. This product is no longer authorized or available for use in Canada.

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Immunogenicity, efficacy and effectiveness

Immunogenicity

All COVID-19 vaccines induce humoral immune responses, including binding and neutralizing antibody responses, and have been shown to produce cellular immune responses in adult populations. The immune responses may vary depending on the product used, number of doses, interval between the doses (longer intervals result in higher antibody titres), the strains against which the immune response is assessed and how immunologically similar the strain is to the vaccine strain, the age and underlying medical conditions of the vaccine recipient (antibody titres may be lower in older adults and those who are immunocompromised due to disease or medication) and the recipient's prior infection and vaccination history. Antibody titres decrease over time since vaccination, although memory responses that can be boosted with vaccination or infection persist.

Antibody titres tend to be higher with vaccines that are antigenically closer to the strain that they are tested against. Clinical studies have shown that XBB.1.5 vaccines had lower antibody responses against more recently circulating JN.1 strains (which are derived from Omicron BA.2.86) than against previously circulating Omicron XBB-related strains. JN.1 strains have continued to evolved to closely related strains, such as KP.2 and KP.3, including KP.3.1.1. Preclinical (animal) studies show that JN.1 and KP.2 encoding vaccines have higher antibody titres against JN.1, KP.2 and KP.3 strains than XBB.1.5 vaccines.

No immunological correlate of protection has been determined for SARS-CoV-2, and therefore the implications of differences in immune responses after COVID-19 vaccination on protection against infection and severe disease, as well as on duration of protection, is uncertain.

Efficacy and effectiveness

Efficacy (how well the vaccine works in clinical trials) and effectiveness (how well the vaccine works in real-world observational studies) of COVID-19 vaccines tends to be lowest against infection, somewhat higher against symptomatic disease and highest against severe disease.

Similar to factors that impact the immune response, vaccine effectiveness may be affected by the vaccine product received, the interval between doses (somewhat better with longer intervals), the time since the most recent dose (as immunity wanes), the circulating strains, the age and health status of the recipient and their prior SARS-CoV-2 infection and vaccination history.

Initial randomized clinical trials using original monovalent vaccines demonstrated high efficacy (over 90%) in adults against symptomatic and severe disease caused by early SARS-CoV-2 strains for both mRNA vaccines (Pfizer-BioNTech Comirnaty and Moderna Spikevax) and the adjuvanted subunit vaccine (Novavax Nuvaxovid).

Studies have also demonstrated efficacy against symptomatic disease of original monovalent vaccines in children, but efficacy was somewhat lower, noting that studies were done later when variants were circulating. Efficacy against severe disease in children 6 months to 4 or 5 years of age could not be assessed because this outcome was rare. Observational studies have also shown vaccine protection against hospitalization due to multisystem inflammatory syndrome in children 5 to 18 years of age.

Vaccine protection decreases over time, particularly against infection and symptomatic disease, and to a lesser extent against severe disease as well. Subsequent doses in those previously vaccinated are intended to increase protection, particularly against severe disease, that may have decreased over time.

Based on early study results, the short-term relative vaccine effectiveness of XBB.1.5 mRNA COVID-19 vaccines in adults has been estimated to be approximately 50 to 60% against symptomatic disease and 60 to 70% against hospitalization. However, similar to previous COVID-19 vaccines, vaccine effectiveness decreased over time, particularly against SARS-CoV-2 infection but also against severe disease, due to waning immunity and sub-lineage changes. Vaccine protection from the JN.1 and KP.2 vaccines will be monitored in real world observational studies as vaccine usage increases.

Protection is higher in those with previous SARS-CoV-2 infection and vaccination (hybrid immunity) than in those who have only been vaccinated or only been infected. A recent Omicron sub-lineage infection combined with COVID-19 vaccination provides the highest degree of protection against future Omicron sub-lineage infection and severe disease.

Vaccine effectiveness against transmission is also measured in some studies. To the extent that COVID-19 vaccines protect against infection, they also prevent transmission as those who are not infected cannot spread infection to others. In addition, vaccination may offer additional protection against transmission even if infection is not prevented as it may reduce viral load and duration of infection. This has previously been demonstrated particularly with a booster dose, although the duration of this protection against transmission remains uncertain and the impact on transmission of the XBB.1.5 and JN.1 and KP.2 vaccines is unknown.

Effectiveness of vaccination against post-COVID-19 condition

Post COVID-19 condition (PCC) is a condition in which symptoms following a SARS-CoV-2 infection persist for more than 8 weeks and are present for 12 or more weeks following the acute phase of the SARS-CoV-2 infection. The predominant symptoms experienced with PCC include fatigue, dyspnea, other respiratory issues, cardiovascular issues, pain, sleep disturbances, decrease in quality of life, cognitive impairment, and anxiety and/or depression. PCC has been estimated to affect approximately 10 to 20% of individuals following COVID-19, with lower rates following Omicron infections than earlier variants.

To the extent that vaccination prevents infection, it also prevents PCC. As well, people who are vaccinated and then become infected may have additional protection against PCC compared to those who are not vaccinated. The impact of COVID-19 vaccinations on PCC continues to be monitored through emerging literature.

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Recommendations for use

COVID-19 JN.1 and KP.2 vaccines (2024-2025) are the currently recommended products for both the primary series (whether starting or completing the series) and for those previously vaccinated.

It is recommended that beginning in the fall of 2024, previously vaccinated and unvaccinated individuals at increased risk of SARS-CoV-2 infection or severe COVID-19 disease should be vaccinated with a JN.1 or KP.2 COVID-19 vaccine as follows:

All individuals 6 months of age and over not listed above may receive an updated (JN.1 or KP.2) vaccine beginning in the fall of 2024.

Schedule for the primary series

Children 6 months to under 5 years of age

Pfizer-BioNTech KP.2 vaccine is not available for those less than 12 years of age. Two (2) doses of Moderna Spikevax KP.2 vaccine with an 8-week interval between doses is the recommended schedule for those 6 months to less than 5 years of age who are not immunocompromised. An additional dose is recommended for individuals who are moderately to severely immunocompromised, with an interval of 4 to 8 weeks between each dose (see Table 1 for schedules and dosages).

The 8-week interval is longer than the authorized interval and is recommended as a better immune response has been associated with a longer interval between doses. For those who are moderately to severely immunocompromised, the 4- to 8-week interval between doses needs to balance a potentially better immune response with longer intervals with the need for earlier protection due to risk of exposure from circulating SARS-CoV-2 and the risk of severe COVID-19 disease.

Those who are moderately to severely immunocompromised are recommended to receive an additional dose in the primary series compared to those who are not immunocompromised in order to help improve the immune response and vaccine effectiveness in this group (based on data from adults). Those who are moderately to severely immunocompromised generally respond less well to COVID-19 vaccines and are at higher risk for severe illness.

If children 6 months to under 5 years of age started the primary series with a non-KP.2 vaccine (i.e., original monovalent, BA.1 bivalent, BA.4/5 bivalent, or XBB.1.5) but did not complete the series, Moderna Spikevax KP.2 vaccine is the recommended product to complete the primary series. If a series was previously started with a Pfizer-BioNTech product, the total number of doses should be as per the Pfizer-BioNTech schedule for children 6 months to less than 5 years of age (3 doses for non-immunocompromised and 4 doses for those who are moderately to severely immunocompromised).

Children who started the primary series at less than 5 years of age (with either a KP.2 or non-KP.2 vaccine) and turn 5 years of age before completing the series, should use the Moderna Spikevax KP.2 mRNA vaccine to complete the primary series as follows:

Individuals 5 years of age and over

For mRNA vaccines, 1 dose of JN.1 or KP.2 vaccine is the recommended schedule for those not previously vaccinated who are not immunocompromised as per the authorized schedule in the product monograph. Moderna Spikevax KP.2 is available for those 6 months of age and over while Pfizer-BioNTech Comirnaty is available for those 12 years of age and over. For Novavax Nuvaxovid JN.1, 2 doses of vaccine are authorized as the primary series for those 12 years of age and over; however, for those in this age group who are not immunocompromised, 1 dose may be used in the primary series.

For individuals who are moderately to severely immunocompromised, 2 doses of COVID-19 vaccine (depending on age and availability, either mRNA vaccine or a protein subunit vaccine may be used) are recommended for the primary series and a third dose may also be offered, with an interval of 4 to 8 weeks between the doses (see Table 1 for schedules and dosages). For those who started the primary series with a non-JN.1/KP.2 vaccine (i.e., original monovalent, BA.1 bivalent, BA.4/5 bivalent or XBB.1.5) but did not complete the series, a JN.1 or KP.2 vaccine is the recommended product to complete the primary series.

Those who are moderately to severely immunocompromised generally respond less well to COVID-19 vaccines and are at higher risk for severe illness. They are recommended to receive additional doses in the primary series compared to those who are not immunocompromised in order to help improve the immune response and vaccine effectiveness in this group (noting that some individuals may not be able to mount a sufficient response even with additional doses). In some cases, a third dose may be needed to improve the immune response; healthcare providers can use clinical discretion to determine the potential benefit of a third dose. However, new recipients of hematopoietic stem cell transplantation (HSCT) and chimeric antigen receptor (CAR) T cell therapy are considered immunologically naïve and should be vaccinated with 3 doses beginning at 3 to 6 months post-HSCT/CAR T-cell therapy, regardless of previous vaccination history, with 4 to 8 weeks between doses.

The 4 to 8-week interval for those who are moderately to severely immunocompromised needs to balance a potentially better immune response with the longer interval with the need for earlier protection due to risk of exposure from circulating SARS-CoV-2 and the risk of severe disease. As well, the risk of myocarditis/pericarditis following the second dose has been determined to be lower with longer intervals between doses.

For children who started a primary series at less than 5 years of age and turn 5 years of age before completing the primary series, see guidance above for Children 6 months to under 5 years of age.

There is no longer a product preference between Moderna Spikevax and Pfizer-BioNTech Comirnaty for unvaccinated individuals 12 to 29 years of age. Previously, Pfizer-BioNTech Comirnaty had been preferred over Moderna Spikevax for the primary series among individuals 12 and 29 years of age due to the higher risk of myocarditis/pericarditis observed following the Moderna Spikevax 100 mcg original monovalent vaccine primary series (especially after the second dose). This product preference has been removed. As compared to the original monovalent primary series, the risk of myocarditis/pericarditis is now expected to be lower due to the use of a 1-dose schedule in most individuals and potentially due to a lower dosage of the available Moderna Spikevax vaccine (50 mcg in the KP.2 formulation compared to 100 mcg in the original monovalent formulation).

There is no longer a preference for mRNA vaccines over protein subunit vaccines for those 12 years of age and over. The previous product preference has been removed because of the increasing amounts of data available regarding the Novavax Nuvaxovid products. However, due to lower overall usage of Novavax Nuvaxovid products to date, there remains less data available about the protein subunit platform compared to the mRNA platform, particularly for people who are pregnant or who are immunocompromised. Additional evidence on the use of the protein subunit COVID-19 vaccine is expected to accumulate over time.

Table 1. Immunization schedule for previously unvaccinated individuals by age starting their vaccinations with authorized 2024-2025 COVID-19 vaccines (that are or may be available)
Age group Immunization scheduleFootnote a Products Recommended intervalFootnote b
Schedule for those not moderately or severely immunocompromised
6 months to under 5 years of age
  • 2-dose Moderna Spikevax
  • 25 mcg Moderna Spikevax
 8 weeks
5 years of age to 11 years of age
  • 1-dose
  • 25 mcg Moderna Spikevax
 Not applicable
12 years of age and older
  • 50 mcg Moderna Spikevax
  • 30 mcg Pfizer-BioNTech Comirnaty
  • 5 mcg Novavax Nuvaxovid
 Not applicable
Schedule for individuals who are moderately to severely immunocompromised
6 months to under 5 years of age
  • 3-dose Moderna Spikevax
  • 25 mcg Moderna Spikevax
 4 to 8 weeks
5 years of age to 11 years of age
  • 2 doses are recommended and a third may be offeredFootnote d
  • 25 mcg Moderna Spikevax
 4 to 8 weeks
12 years of age and older
  • 2 doses are recommended and a third may be offeredFootnote d
  • 50 mcg Moderna Spikevax
  • 30 mcg Pfizer-BioNTech Comirnaty
  • 5 mcg Novavax Nuvaxovid
 4 to 8 weeks
a

See text under Schedule for the primary series regarding individuals who started but did not complete a primary series with a vaccine that was not a JN.1/KP.2 formulation.

Return to footnote a referrer

b

For individuals with recent SARS-CoV-2 infection, these are also the suggested intervals between SARS-COV-2 infection and receiving doses in a primary series of COVID-19 vaccine.

Return to footnote b referrer

c

For Novavax Nuvaxovid JN.1, 2 doses of vaccine are authorized as the primary series for those 12 years of age and over, however, for those in this age group who are not immunocompromised, 1 dose may be used in the primary series.

Return to footnote c referrer

d

New recipients of hematopoietic stem cell transplantation (HSCT) and chimeric antigen receptor (CAR) T cell therapy should be vaccinated with 3 doses, regardless of previous vaccination history, with 4 to 8 weeks between doses.

Return to footnote d referrer

Schedule for those previously vaccinated

The recommended interval is 6 months from the last COVID-19 vaccine dose. However, a shorter interval of at least 3 months may be used. For individuals with test-confirmed SARS-CoV-2 infection, these same intervals (i.e., 6 months, with a minimum of 3 months) from test-confirmed infection to COVID-19 vaccination may be considered.

As with the primary series, for ages where both platforms are authorized, either mRNA or the protein subunit vaccines can be used for those who are previously vaccinated, with no preference between vaccine platforms. As noted above, there is more data available for mRNA vaccines, particularly for people who are pregnant or who are immunocompromised. Additional evidence on the use of the protein subunit COVID-19 vaccine is expected to accumulate over time.

For information on the management of errors and deviations, see PHAC's resource: Quick reference guide on the use of COVID-19 vaccines: Managing vaccine administration errors or deviations for additional guidance.

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Vaccination of specific populations

Pregnancy and breastfeeding

Compared to non-pregnant persons, SARS-CoV-2 infection in pregnancy is associated with increased risk of hospitalization and admission to an ICU. SARS-CoV-2 infection during pregnancy is also associated with an increased risk in the neonate of preterm birth, low birth weight and admission to a neonatal intensive care unit (NICU). Vaccination helps to protect the person who is pregnant and vaccination during pregnancy also lowers the risk of hospitalization for their newborn.

Recommendations

People who are pregnant or breastfeeding are recommended to be vaccinated as per the Recommendation for use section, for both those unvaccinated and those previously vaccinated. COVID-19 vaccines can be given at any stage of pregnancy.

Pregnancy is included in the group of individuals who should receive COVID-19 vaccine beginning in fall 2024 with the updated vaccine (2024-2025 products). At this time, there is no recommendation for a dose of COVID-19 vaccine in every pregnancy.

Either mRNA or protein subunit vaccines may be used for people who are pregnant. However, there is more data available for mRNA vaccines than the protein subunit vaccine for people who are pregnant.

Considerations

Pregnant or breastfeeding individuals were excluded from COVID-19 vaccine clinical trials. However, analysis of data collected through international COVID-19 immunization registries to date have not revealed any maternal or neonatal safety signals.

Informed consent should include discussion that there is real-world evidence on the safety profile and effectiveness of mRNA vaccination with large numbers of individuals who are pregnant or breastfeeding, but currently less evidence on the use of the protein subunit vaccine.

Rates of adverse effects are similar in people who are pregnant or breastfeeding and those who are not pregnant or breastfeeding. Studies have not found any impacts of mRNA COVID-19 vaccination on the infant/child being fed human milk or on milk production or excretion. Vaccination during pregnancy does not increase risk for adverse pregnancy/birth outcomes, including miscarriage, stillbirth, low birth weight, preterm birth or NICU admission.

Evidence suggests that COVID-19 mRNA vaccination during pregnancy results in comparable antibody titres to those generated in non-pregnant women. Maternal IgG humoral response to mRNA COVID-19 vaccines transfers across the placenta to the fetus, leading to a significant and potentially protective antibody titre in the neonatal bloodstream 1 week after the second dose. Infants of people who received the second dose of a primary series or a booster dose during pregnancy had a lower risk of hospitalization with COVID-19 (including Omicron) compared to infants born to individuals who were unvaccinated.

The effect was greater with the booster dose than the second dose in a primary series and if the dose was given later in the pregnancy as opposed to earlier. The protection from maternal vaccination against infant hospitalization decreases over time since birth.

Observational studies consistently show that both anti-spike IgG and IgA are present in breastmilk for at least 6 weeks after maternal vaccination with mRNA vaccines. The protection against disease as a result of breastfeeding is currently unknown.

Individuals who have received a COVID-19 vaccine during pregnancy are encouraged to enroll in a COVID-19 vaccine pregnancy registry (see Table 2).

There is a Canadian COVID-19 Vaccine Registry for Pregnant and Lactating Individuals, hosted at the University of British Columbia to assess the safety and effectiveness of COVID-19 vaccines.

Table 2. Pregnancy registry information by vaccine product
Vaccine product Registry information
Pfizer-BioNTech Comirnaty COVID-19 vaccines Pfizer-BioNTech does not have a vaccine registry for pregnant persons. Individuals who are vaccinated with the Pfizer-BioNTech COVID-19 vaccine during pregnancy are encouraged to enroll into the Canadian COVID-19 Vaccine Registry for Pregnant and Lactating Individuals described above.
Moderna Spikevax COVID-19 vaccines There is a vaccine registry that monitors pregnancy outcomes in persons vaccinated with the Moderna COVID-19 vaccine during pregnancy. Individuals who are vaccinated with the Moderna COVID-19 vaccine during pregnancy are encouraged to enroll in the registry by calling 1-866-MODERNA (1-866-663-3762).
Novavax Nuvaxovid COVID-19 vaccines There is a vaccine registry that monitors pregnancy outcomes in persons vaccinated with NUVAXOVID during pregnancy. Individuals who are vaccinated with NUVAXOVID during pregnancy are encouraged to enroll in the registry by visiting C-VIPER: COVID-19 Vaccines International Pregnancy Exposure Registry.

Refer to Immunization in pregnancy and breastfeeding in Part 3 for additional general information.

Individuals previously infected with SARS-CoV-2

The immune response due to prior infection may vary due to factors such as the severity of infection, age, presence of comorbidities, the SARS-CoV-2 variant causing the infection, time since the infection and vaccination history. People with both SARS-CoV-2 infection and COVID-19 vaccination are said to have "hybrid immunity" and have the best protection against SARS-CoV-2 infection and severe disease compared to those with either infection or vaccination alone.

Recommendations

Vaccination is recommended in those who are previously infected as per the Recommendation for use section.

For those with a test-confirmed SARS-CoV-2 infection, the interval that can be considered from infection to vaccination in the primary series is the same as the recommended intervals between COVID-19 vaccine doses (8 weeks for those who are not immunocompromised, and 4 to 8 weeks for those who are moderately to severely immunocompromised) [see Recommended interval in Table 1].

For those who are previously vaccinated and who test positive for SARS-CoV-2, an interval of 6 months, with a minimum of 3 months from test-confirmed infection to COVID-19 vaccination may be considered.

These suggested intervals from infection to COVID-19 vaccination serve as a guide and are based on immunological principles and expert opinion and may change as evidence emerges. Clinical discretion is advised for immunizers.

Individuals with a history of multisystem inflammatory syndrome in children or adults (MIS-C or MIS-A) should wait to be vaccinated for at least 90 days from diagnosis or clinical recovery, whichever is longer.

Considerations

Testing for previous SARS-CoV-2 infection is not needed prior to COVID-19 vaccination.

Current evidence suggests protection is more robust and longer lasting with vaccination in previously infected individuals compared to immunity from SARS-CoV-2 infection alone.

A longer interval between infection and vaccination may result in a better immune response as this allows time for the response from the infection to mature in breadth and strength, and for circulating antibodies from the infection to decrease, thus avoiding immune interference when the vaccine is administered.

When considering the suggested intervals outlined above, biological and social risk factors for exposure (e.g., local epidemiology, living settings) and severe disease should also be taken into account.

COVID-19 vaccination in individuals previously infected with SARS-CoV-2 has a good safety profile and is well tolerated. Limited evidence suggests reactogenicity may be slightly increased in individuals previously infected with SARS-CoV-2 compared to those with no history of previous infection, however this evidence is limited to the primary series and variants prior to Omicron.

Immunocompromised persons

Individuals with immunocompromising conditions, including those receiving immunosuppressive therapy, are at increased risk for prolonged infection, serious complications from SARS-CoV-2 infection as well as reduced immune responses to vaccination and reduced vaccine effectiveness. Additional doses may help improve the immune response and vaccine effectiveness in people who are moderately to severely immunocompromised.

Recommendations

People who are moderately to severely immunocompromised are recommended to be vaccinated as per the Recommendation for use section. They are included in the group of people who should be vaccinated with an updated vaccine (JN.1 or KP.2) beginning in the fall of 2024. Moderna Spikevax is available for those 6 months of age and over and Pfizer-BioNTech Comirnaty is available for those 12 years of age and over. Novavax Nuvaxovid is authorized for use in those 12 years of age and older.

For those who are moderately to severely immunocompromised, the primary series of updated 2024-2025 COVID-19 vaccines is as follows, with an interval of 4 to 8 weeks between doses:

Healthcare providers can use clinical discretion to determine the potential benefit of a third dose for those 5 years of age and over who are moderately to severely immunocompromised. However, new recipients of hematopoietic stem cell transplantation (HSCT) and chimeric antigen receptor (CAR) T cell therapy should be vaccinated with 3 doses beginning at 3 to 6 months post-HSCT/CAR T-cell therapy, regardless of previous vaccination history. Please refer to Immunization of immunocompromised persons in Part 3 for specific immunization recommendations for these populations.

For those previously vaccinated, the recommended interval is 6 months from the last COVID-19 vaccine dose. However, a shorter interval of at least 3 months may be used.

Either mRNA or protein subunit vaccines may be used for people who are immunocompromised. However, there is more data available for mRNA vaccines than the protein subunit vaccine for people who are immunocompromised.

Considerations

Immunocompromised individuals, including those receiving immunosuppressive therapy, are at increased risk for prolonged infection and serious complications from SARS-CoV-2 infection. Numerous studies have shown that immunogenicity is substantially decreased in some immunocompromised individuals when compared to healthy vaccine recipients. Observational studies in adults with complete 1 or 2 dose series, show lower vaccine effectiveness against SARS-CoV-2 infection and COVID-19 disease in immunocompromised adults when compared to the general population. Additional doses are recommended to help improve the immune response and vaccine effectiveness, however some individuals may not be able to mount a sufficient response even with additional doses.

In considering the 4 to 8-week interval between vaccine doses (or infection and vaccine doses) in the primary series, a longer interval is likely to result in a better immune response. However, moderately to severely immunocompromised individuals may remain susceptible during the primary series before the next dose is administered; therefore, the risk of exposure (including local transmission of SARS-CoV-2) and risk of severe disease (e.g., underlying high risk medical condition) should be taken into account when considering the intervals in a primary series. For adolescents and young adults, it should also be noted that the risk of myocarditis/pericarditis is lower with longer intervals between doses in the primary series.

Indirect data from general adult populations (18 years of age and older) with original mRNA COVID-19 vaccines suggested Moderna Spikevax original (100 mcg) may result in higher vaccine effectiveness after a 2-dose primary series compared to Pfizer-BioNTech Comirnaty original (30 mcg). Moderna Spikevax original (100 mcg) was also associated with a higher seroconversion rate and higher total antibody titres than Pfizer-BioNTech (30 mg) among adult patients who are immunocompromised. It is unknown whether this enhanced immunogenicity would also be observed with Moderna Spikevax KP.2 vaccine compared to Pfizer-BioNTech Comirnaty Omicron KP.2 vaccine at the different age-based dosages.

A vaccine series should ideally be completed at least 2 weeks before initiation of immunosuppressive therapies where possible.

Moderately to severely immunocompromised includes individuals with the following conditions:

A range of factors can impact the relative degree of immunocompromise and response to COVID-19 vaccines, and clinical and public health judgement should be applied. Jurisdictions may modify the above list based on population considerations.

In observational studies and clinical trials, humoral and cellular immune responses were similar between fully vaccinated people living with HIV on antiretroviral therapy and those who were HIV-negative.

Based on observational studies, the frequency and severity of adverse events following immunization (AEFI) with an mRNA COVID-19 vaccine in certain immunocompromised populations were comparable to those of non-immunosuppressed individuals. No worsening of underlying disease was reported after immunization.

Refer to Immunization of immunocompromised persons in Part 3 for additional information, including a suggested definition of high dose steroids and for additional guidance on vaccination with COVID-19 vaccines for individuals pre- and post-hematopoietic stem cell transplantation (HSCT) and for chimeric antigen receptor (CAR) T cell therapy recipients.

Travellers

Travellers are recommended to be vaccinated as per the Recommendations for use section.

Travellers who are due for COVID-19 vaccinations should optimally complete these at least 2 weeks before departure. Travellers should verify the travel requirements in place at their destination(s). For more information, refer to the Committee to Advise on Tropical Medicine and Travel (CATMAT) Statement on COVID-19 and International Travel.

Persons new to Canada

Persons new to Canada who are planning to live, work or study in Canada should be vaccinated as per the Recommendations for use section.

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Serologic testing

Serologic testing is not needed before or after immunization with COVID-19 vaccine.

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Administration practices

Dose and route of administration of available products

The text and Table 3 summarize authorized 2024-2025 vaccine products that are or may be available.

Dose

Pfizer-BioNTech Comirnaty 2024-2025 COVID-19 vaccine

There are several presentations of Pfizer-BioNTech Comirnaty COVID-19 vaccine authorized for use. Only the presentations available in Canada are listed below.

Pfizer-BioNTech Comirnaty 2024-2025 COVID-19 vaccine (30 mcg)

This presentation has a grey cap and a grey label border and is authorized for use in individuals 12 years of age and older.

No dilution is required.

Each dose is 0.3 mL, containing 30 mcg of SARS-CoV-2 KP.2 spike protein mRNA.

Special precaution should be taken to ensure the correct dose is taken from the multi-dose vial.

Moderna Spikevax 2024-2025 COVID-19 vaccine

There is one presentation of Moderna Spikevax KP.2 authorized for use in individuals 6 months of age and older, supplied as a 0.10 mg/mL suspension in a 2.5 mL multidose vial with a royal blue cap and coral blue label border.

No dilution is required.

The volume required differs by age: 0.25 mL (25 mcg) for 6 months to 11 years and 0.5 mL (50 mcg) for 12 years of age and over.

Novavax Nuvaxovid 2024-25 COVID-19 vaccine

The product is authorized for 12 years of age and over and has a blue-coloured cap. Vials contain 5 mcg/0.5 mL in a 2.5 mL multidose vial. Each dose is 0.5 mL, containing 5 mcg SARS-CoV-2 recombinant JN.1 strain spike protein.

The product comes premixed with the Matrix-M adjuvant. No dilution or reconstitution is required.

Table 3. Overview of authorized 2024-2025 vaccines (that are or may be availableFootnote a), by product and age
Age group Dose Description Dilution required
Pfizer- BioNTech Comirnaty KP.2
12 years of age and older 30 mcg (0.3 mL) Cap and label colour: Grey No
Moderna Spikevax KP.2
6 months to 11 years of age 25 mcg (0.25 mL)

0.10 mg/mL
Cap colour: Royal blue;
Label colour: Coral blue

 No
12 years of age and older 50 mcg (0.5 mL)
Novavax Nuvaxovid JN.1
12 years of age and older 5 mcg (0.5 mL)

5 mcg/0.5 mL
Cap colour: Blue

 No
a

The following products are authorized in Canada but are not available: Pfizer-BioNTech Comirnaty KP.2 vaccine at 3 mcg for 6 months to less than 5 years of age and Pfizer-BioNTech Comirnaty KP.2 vaccine at 10 mcg for 5 to 11 years of age. At the time of publishing this updated chapter, the availability of Novavax Nuvaxovid JN.1 vaccine for 12 years of age and over is uncertain.

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Route of administration

COVID-19 vaccines are given as an intramuscular (IM) injection. The deltoid muscle of the arm is the preferred injection site in adolescents and adults, unless the muscle mass is not adequate or vaccination in that site is not possible, in which case the anterolateral thigh can be used.

Refer to Vaccine administration practices in Part 1 for additional general information, including recommended routes of administration for children.

If an error in vaccine administration occurs, refer to Managing COVID-19 vaccine administration errors or deviations for guidance.

Interchangeability of vaccines

Any of the three available 2024-2025 COVID-19 vaccines can be used to complete a primary series started with another product, and as subsequent doses in those previously vaccinated. When a JN.1/KP.2 vaccine is used to complete the primary series started with another COVID-19 vaccine formulation (either original monovalent wild type-containing, bivalent vaccine or XBB.1.5), the previous dose(s) should be counted, and the series need not be restarted.

Children 6 months to less than 5 years of age, who started but did not complete their primary series, where at least one dose was a previous formulation of Pfizer-BioNTech Comirnaty vaccine, should complete their primary series with Moderna Spikevax KP.2 vaccine; they should receive the total number of doses (KP.2 and non-KP.2 combined) as recommended for a Pfizer-BioNTech schedule (i.e., 3 doses for children who are not immunocompromised, and 4 doses for those who are moderately to severely immunocompromised).

Concurrent administration with other vaccines

For individuals 6 months of age and older, COVID-19 vaccines may be given concurrently (i.e., same day), or at any time before or after non-COVID-19 vaccines (including live and non-live vaccines).

Concurrent administration will reduce barriers to the provision of routine childhood immunizations and seasonal influenza immunization. Studies and surveillance activities to assess the safety, immunogenicity and effectiveness of concurrent administration of COVID-19 vaccines with other vaccines have been reassuring to date and are ongoing. Most studies report on the concurrent administration of influenza and COVID-19 vaccines, with the majority of these studies reporting non-inferior immune responses to COVID-19 and influenza after concurrent administration compared to after separate administration. In a few studies where immune responses to COVID-19 were not non-inferior after concurrent administration; the significance of these decreased immune responses and implications on vaccine effectiveness, if any, are unknown. Studies on vaccine effectiveness with concurrent vaccine administration are limited to date, but suggest that effectiveness against COVID-19 and influenza-related outpatient visits, emergency department visits and hospitalizations are similar with concurrent administration compared to separate administration.

There are no established safety issues associated with concurrent administration of COVID-19 vaccines with other vaccines. In some studies, reactogenicity after concurrent administration of COVID-19 vaccines and influenza vaccines was increased compared to influenza vaccination alone, but comparable to COVID-19 vaccination alone.

If more than one type of vaccine is administered at a single visit, they should be administered at different injection sites using separate injection equipment. Preferably this is in different limbs, however if the same limb must be used, the injection sites should be separated by at least 2.5 cm (1 inch). COVID-19 vaccines should never be mixed in the same syringe as other vaccines.

Informed consent should include a discussion of the benefits and risks given the limited data available on administration of COVID-19 vaccines at the same time as, or shortly before or after, other vaccines.

Refer to Timing of vaccine administration in Part 1 for additional general information on concurrent administration of other vaccines.

Pre-vaccination counselling

Prior to providing a COVID-19 vaccine, informed consent should include discussion about frequently occurring minor adverse events and the risks and symptoms of potential rare severe adverse events.

Anyone receiving any COVID-19 vaccine should be informed of the risks associated with COVID-19 vaccines (myocarditis/pericarditis and anaphylaxis) and be advised to seek medical attention if they develop signs or symptoms suggestive of these conditions.

Prophylactic oral analgesics or antipyretics (e.g., acetaminophen or ibuprofen) should not be routinely used before or at the time of vaccination, but their use is not a contraindication to vaccination. There is currently no evidence of benefit from administration of oral analgesics for the prevention of immunization injection pain or systemic reactions.

Refer to Safety and adverse events for further information.

Post-vaccination counselling

Vaccine recipients should be kept under observation for at least 15 minutes after immunization; 30 minutes is a preferred interval when there is a specific concern about a possible vaccine reaction (see Other allergies for additional information).

All vaccine recipients should be instructed to seek medical care immediately if they develop signs or symptoms of a serious adverse event or an allergic reaction following vaccination.

Oral analgesics or antipyretics may be considered for the management of adverse events (e.g., pain or fever, respectively), if they occur after vaccination. Analgesics and antipyretics were used in clinical trials of COVID-19 vaccines for the management of pain and/or fever after vaccination.

Refer to Vaccine administration practices in Part 1 for additional information on pre- and post-vaccination counseling.

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Storage requirements

For information on storage, handling and transport of frozen and thawed vaccine vials, refer to the Overview of key features of COVID-19 vaccines authorized in Canada.

For additional information, consult the product leaflet or information contained within the product monograph available through Health Canada's Drug Product Database. Refer to Storage and handling of immunizing agents in Part 1 for additional general information.

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Safety and adverse events

Evidence on vaccine safety is available from COVID-19 clinical trials and ongoing national and international COVID-19 vaccine safety monitoring. The clinical trials solicited adverse events for defined lengths of time following a vaccine dose, as well as collecting unsolicited and serious events.

For reported side effects following COVID-19 vaccination in Canada, refer to the PHAC AEFI report.

Refer to Vaccine safety and pharmacovigilance and Adverse events following immunization (AEFI) in Part 2 for additional information on vaccine safety and for definitions of AEFIs, and reporting of an AEFI to public health.

For individuals who develop AEFIs following COVID-19 vaccination, refer to the Contraindications and precautions section for advice on future vaccinations.

Very common and common adverse events

Common adverse events are defined as those that occur in 1% to less than 10% of vaccine recipients; very common adverse events occur in 10% or more of vaccine recipients.

Local

Local adverse events were usually mild or moderate and resolved within a few days of vaccination. Pain at the injection site was very common. Redness and swelling were common or very common after administration of any authorized COVID-19 vaccine. Localized axillary (or groin) swelling and tenderness (lymphadenopathy) was a solicited adverse event in the Moderna Spikevax original COVID-19 vaccine clinical trial and was very common after administration of that vaccine.

Systemic

Systemic adverse events were usually mild or moderate and resolved within a few days of vaccination. Fatigue, headache, muscle pain, chills, and joint pain were all either common or very common after the administration of any authorized COVID-19 vaccine.

The most frequent reactions reported for children aged 6 months to 2 years included irritability or crying, sleepiness, and loss of appetite. These reactions are common after childhood vaccination.

Adverse events in individuals previously infected with SARS-CoV-2

Limited evidence suggests reactogenicity may be slightly increased in individuals previously infected with SARS-CoV-2 compared to those with no history of previous infection; however, this evidence is limited to the primary series and infection with variants prior to Omicron.

Adverse events following updated mRNA COVID-19 vaccines

Evidence on vaccine safety is available from COVID-19 clinical trials and ongoing national and international COVID-19 vaccine safety monitoring. In clinical trials, booster doses of updated COVID-19 vaccines (bivalent original plus Omicron or monovalent XBB.1.5) have been shown to have similar reactogenicity as booster doses of original COVID-19 vaccines. No new adverse events have been identified with the use of the XBB.1.5 COVID-19 vaccines. Post-market safety surveillance data suggests that updated COVID-19 vaccines are tolerated with a similar safety profile as original mRNA COVID-19 vaccines.

Uncommon, rare and very rare adverse events

Uncommon adverse events occur in 0.1% to less than 1% of vaccine recipients. Rare and very rare adverse events occur in 0.01% to less than 0.1% and less than 0.01% of vaccine recipients, respectively. The probability of detection of very rare adverse events in clinical trials is low given clinical trial sample sizes; therefore, ongoing pharmacovigilance is essential to detect events with these frequencies if they are occurring.

Lymphadenopathy

Lymphadenopathy was an unsolicited event that was uncommonly reported after administration of the Pfizer-BioNTech Comirnaty original (both 10 mcg and 30 mcg formulations) in clinical trials. As noted above, lymphadenopathy was a solicited adverse event in the clinical trials for Moderna Spikevax original and was very commonly reported.

Myocarditis and/or pericarditis following vaccination with mRNA and other COVID-19 vaccines

Rare cases of myocarditis (inflammation of the heart muscle) and/or pericarditis (inflammation of the lining around the heart) have been reported following vaccination with mRNA and protein subunit COVID-19 vaccines.

Cases following mRNA COVID-19 vaccination are consistently reported to have occurred:

Symptoms of myocarditis/pericarditis may include:

Analyses of primary series surveillance data in Canada, US and European Nordic countries suggests a higher rate of myocarditis/pericarditis cases reported after vaccination with Moderna Spikevax original (100 mcg) compared to Pfizer-BioNTech Comirnaty original (30 mcg) vaccine especially among 12 to 29 year old males following a second dose of vaccine. Longer intervals between doses have been noted to result in lower rates of myocarditis/pericarditis. The rates of myocarditis/pericarditis specific to the KP.2 mRNA vaccines are currently unknown.

Myocarditis unrelated to exposure to COVID-19 disease or COVID-19 vaccines is typically less common in younger children 5 to 11 years of age. Among children 5 to 11 years of age following vaccination with Pfizer-BioNTech Comirnaty original (10 mcg), very rare cases were most often reported following dose 2 and among males. The risk of myocarditis or pericarditis with Moderna Spikevax original (50 mcg) in children 6 to 11 years of age is unknown.

Available post-market vaccine safety data from V-safe, Vaccine Safety Datalink (VSD) and Vaccine Adverse Event Reporting System (VAERS) in the US as of September 2022 show that the Moderna Spikevax (25 mcg) and Pfizer-BioNTech Comirnaty (3 mcg) mRNA COVID-19 vaccines are well tolerated among children aged 6 months to 5 years. No safety signals (including myocarditis) have been identified after administration of about 1.5 million vaccine doses.

Evidence from bivalent and original mRNA COVID-19 vaccines across different age groups show that the risk of myocarditis is lower following boosters compared to dose 2 of the primary series, and that no product-specific difference in the risk of myocarditis has been identified following a booster dose at this time, including in adolescents 12 to 17 years of age. However, the use of Moderna Spikevax COVID-19 vaccines had been limited in those 5 to 17 years of age. While long-term follow-up is ongoing, available data indicate that the majority of individuals who reported myocarditis/pericarditis after mRNA COVID-19 vaccination, though requiring hospitalization, have responded well to conservative therapy and tend to recover quickly.

A further breakdown of the rates of myocarditis/pericarditis after protein subunit vaccines, specifically Novavax Nuvaxovid original, by age group (including among adolescents), sex and dose number are not available due to the relatively low number of doses given and reported cases.

Healthcare providers should consider myocarditis/pericarditis in their evaluation if the patient presents with clinically compatible symptoms (e.g., chest pain, shortness of breath, palpitations) after a COVID-19 vaccine regardless of timing from vaccination to symptoms onset. Investigations include electrocardiogram, serum troponins and echocardiogram. Abnormal electrocardiogram findings and elevated troponin levels have been frequently noted with myocarditis/pericarditis following mRNA vaccine.

Consultation with a cardiologist, infectious disease specialist, or internal medicine specialist may be advisable to assist in this evaluation, particularly to investigate the many potential causes of myocarditis and pericarditis. Investigations may include diagnostic testing for acute SARS-CoV-2 infection (e.g., PCR testing), prior SARS-CoV-2 infection and consideration of other potential infectious or non-infectious etiologies including auto-immune conditions.

Refer to the Contraindications and precautions section for advice on re-vaccination of individuals who developed myocarditis/pericarditis after a COVID-19 vaccine.

Bell's palsy

Very rare cases of Bell's palsy (typically temporary weakness or paralysis on one side of the face) have been reported following vaccination with mRNA COVID-19 vaccines (Pfizer-BioNTech Comirnaty original or Moderna Spikevax original) among individuals aged 12 years and older. The Pfizer-BioNTech Comirnaty and Moderna Spikevax product monographs list Bell's palsy as a possible adverse effect. However, available evidence is not currently sufficient to support a causal relationship between the mRNA vaccines and Bell's palsy. Symptoms of Bell's palsy appear suddenly and generally start to improve after a few weeks. The exact cause of Bell's palsy is unknown. It's believed to be the result of swelling and inflammation of the nerve that controls muscles on the face.

Symptoms of Bell's palsy may include:

Individuals should seek medical attention if they develop symptoms of Bell's palsy following receipt of COVID-19 vaccines. Healthcare providers should consider Bell's palsy in their evaluation if the patient presents with clinically compatible symptoms after a COVID-19 vaccine. Investigations should exclude other potential causes of facial paralysis.

Multisystem inflammatory syndrome in children or in adults (MIS-C or MIS-A) following vaccination with an mRNA COVID-19 vaccine

Multisystem inflammatory syndrome in children (MIS-C) is a rare condition which usually occurs 2 to 6 weeks after a child is infected with SARS-CoV-2. MIS-C causes inflammation in various parts of the body, including the heart, lungs, kidneys, brain, skin, eyes and/or gastrointestinal tract. MIS-C is rare and requires hospitalization, but most children recover. Multisystem inflammatory syndrome in adults (MIS-A) is a similar syndrome that very rarely affects adults.

During the manufacturer-led clinical trials for mRNA COVID-19 vaccines, no cases of MIS-C were reported among children or adolescents. However, any rare or very rare adverse effects that occur at a frequency less often than 1 in 10,000 would likely not be detected due to the limitations of the trial size.

Very rare cases of MIS-C or MIS-A have been reported following vaccination with COVID-19 mRNA vaccines in Canada and internationally among individuals aged 12 years and older. In October 2021, the European Medicines Agency (EMA) Pharmacovigilance Risk Assessment Committee (EMA-PRAC) issued a statement that there is currently insufficient evidence regarding a possible link between mRNA COVID-19 vaccines and very rare cases of MIS-C or MIS-A.

Severe immediate allergic reactions (e.g., anaphylaxis) following vaccination with COVID-19 vaccines

Anaphylaxis is a very rare, severe, life-threatening allergic reaction typically with a rapid onset that involves multiple organ systems and can progress rapidly. Symptoms and signs of anaphylaxis may include but are not limited to:

Very rare cases of severe immediate allergic reactions (e.g., anaphylaxis) have been reported following vaccination with mRNA and protein subunit COVID-19 vaccines. Most of the reported cases have occurred within 30 minutes of vaccination.

Individuals tend to recover quickly with appropriate treatment and there have been no fatalities nor long-term morbidity observed with any of these severe immediate allergic reactions in Canada.

Studies have shown that individuals with a severe immediate allergic reaction after a previous dose of mRNA vaccine can be re-vaccinated with the same vaccine or another mRNA COVID-19 vaccine following an appropriate medical assessment. In these studies, re-vaccination was safe and well tolerated with predominantly no, or mild, reactions after re-vaccination when provided in a controlled environment. Available evidence also suggests that most of the reported severe immediate allergic reactions following mRNA COVID-19 vaccines are likely not immunoglobulin E (IgE)-mediated and therefore have a low risk of recurrence following future vaccine doses. Refer to Precautions below for additional information.

Refer to Anaphylaxis and other acute reactions following vaccination in Part 2 for information on the management of anaphylaxis post-vaccination.

Refer to the Contraindications and precautions section for advice on re-vaccination of individuals who had an anaphylactic reaction after vaccination and for vaccination advice for those allergic to components of the COVID-19 vaccines.

Adverse events following vaccination with viral vector vaccines

A number of serious adverse events were observed after the previously available viral vector vaccines Vaxzevria, COVISHIELD and Jcovden (see Preparations authorized for use in Canada).

Venous thromboembolism (VTE) has been observed rarely following vaccination with the Janssen Jcovden COVID-19 Vaccine.

Guillain-Barré syndrome (GBS), a rare but potentially serious immune-mediated neurologic disorder, was identified as having an increased risk following vaccination with the viral vector COVID-19 vaccines (AstraZeneca Vaxzevria and Janssen Jcovden).

Cases of immune thrombocytopenia (ITP) with very low platelet levels (<20,000 per µL) have been reported very rarely after vaccination with Janssen Jcovden and AstraZeneca Vaxzevria COVID-19 vaccines, usually within the first four weeks after vaccination.

Very rare cases of capillary leak syndrome (CLS) have been reported following immunization with the viral vector COVID-19 vaccines (AstraZeneca Vaxzevria and Janssen Jcovden). CLS is a very rare, serious condition that causes fluid leakage from capillaries.

Very rare cases of serious blood clots or thrombosis (at unusual sites such as cerebral venous sinus thrombosis, splanchnic vein thrombosis, as well as arterial thrombosis) associated with thrombocytopenia have been reported following vaccination with viral vector COVID-19 vaccines. These were known as thrombosis with thrombocytopenia syndrome (TTS). A subset of cases of TTS that tested positive for a biomarker, anti-PF4 (antibodies to platelet factor 4-polyanion complexes), were referred to as vaccine-induced immune thrombotic thrombocytopenia (VITT). The exact mechanism by which the viral vector COVID-19 vaccines trigger this syndrome is still under investigation.

Guidance on reporting adverse events following immunization (AEFI)

Vaccine providers are asked to report AEFIs through local public health departments and to follow AEFI reporting requirements that are specific to their province or territory. In general, any serious (defined as resulting in hospitalization, permanent disability or death) or unexpected adverse event that is temporally related to vaccination should be reported. Refer to Reporting AEFI in Canada for additional information on the completion and submission of AEFI reports.

At the international level, the Brighton Collaboration has developed a list of Adverse Events of Special Interest (AESI). AESI are pre-specified medically significant events that have the potential to be causally associated with a vaccine product. Refer to Brighton Collaboration: COVID-19 resources and tools for the list of AESIs and for case definitions of specific AEFIs.

Refer to Adverse events following immunization (AEFI) in Part 2 for additional information on definitions, reporting, investigating and managing, and causality assessments for AEFIs.

Refer to the PHAC weekly report for reported adverse events following COVID-19 vaccination in Canada.

Contraindications and precautions

Contraindications

In general, vaccines are contraindicated in individuals who are hypersensitive to the active ingredient or to any ingredient in the formulation, including any non-medicinal ingredient, or component of the container. For COVID-19 vaccines, in some cases, individuals with a known or suspected hypersensitivity may receive the vaccine under medical supervision. See Precautions for more details.

See the Contraindications and precautions chapter for more information on allergies.

Precautions

Hypersensitivity and allergies

Severe immediate allergic reaction (e.g., anaphylaxis) to an mRNA COVID-19 vaccine

In individuals with a history of a severe, immediate (4 hours or less following vaccination) allergic reaction after previous administration of an mRNA COVID-19 vaccine, re-vaccination may be offered with the same vaccine or the same platform if a risk assessment deems that the benefits outweigh the potential risks for the individual and if informed consent is provided. Consultation with an allergist or other appropriate physician should be sought prior to re-vaccination.

If re-vaccinated, vaccine administration should be done in a controlled setting with expertise and equipment to manage anaphylaxis. Individuals should be observed for at least 30 minutes after re-vaccination. For example, a longer period of observation is warranted for individuals exhibiting any symptom suggestive of an evolving AEFI at the end of the 30-minute observation period.

Confirmed allergies to a component of a COVID-19 vaccine

Ingredients of authorized COVID-19 vaccines that have been associated with allergic reactions in other products are polyethylene glycol (PEG), tromethamine (trometamol or Tris) and polysorbate 80. There is a potential of cross-reactive hypersensitivity between PEG and polysorbate.

All mRNA vaccines (Pfizer BioNTech and Moderna Spikevax) have polyethylene glycol (PEG) and tromethamine (trometamol or Tris) but no polysorbate 80.

Novavax Nuvaxovid has polysorbate 80 but no polyethylene glycol (PEG) or tromethamine (trometamol or Tris).

In individuals with a confirmed severe, immediate (≤4 hours following exposure) allergy (e.g., anaphylaxis) to a component of a specific COVID-19 vaccine (e.g., PEG), or its container, consultation with an allergist is recommended before receiving the specific COVID-19 vaccine. Individuals with a known or suspected serious allergy to a component of a COVID-19 vaccine for whom the vaccine is felt to be appropriate should be observed for at least 30 minutes after vaccination, if they receive a vaccine containing that component or have a proven serious allergic reaction to any injectable therapy (see Other allergy section below).

It is important to note that other, less serious reactions may mimic allergic reactions (e.g., vasovagal syncope) and vaccination is not contraindicated in these cases.

Mild to moderate immediate allergic reactions to a COVID-19 vaccine or a vaccine excipient

In individuals with mild to moderate immediate allergic reactions (defined as limited in the scope of symptoms and involvement of organ systems or even localized to the site of administration) to a previous dose of mRNA COVID-19 vaccine or any of its components, re-vaccination may be offered with the same vaccine or the same platform (i.e., mRNA). Assessment by a physician or nurse with expertise in immunization may be warranted prior to re-immunization. They should also be observed for an extended period of at least 30 minutes after re-vaccination.

Other allergies

The following individuals may be routinely vaccinated with COVID-19 vaccines with the following recommended observation periods.

30-minute post-vaccination observation period:

15-minute post-vaccination observation period:

Acute illness

Vaccination of individuals who may be currently infected with SARS-CoV-2 is not known to have a detrimental effect on the illness. However, vaccination should be deferred in individuals with confirmed or suspected SARS-CoV-2 infection, or those with respiratory symptoms, to minimize the risk of transmission of SARS-CoV-2 and other respiratory viruses at an immunization clinic/venue. If any person is identified with symptoms on arrival at the venue, they should not be immunized and should be instructed to seek medical and public health advice as appropriate and follow current local public health measures.

See Individuals previously infected with SARS-CoV-2 section for additional information.

Bleeding disorders

In individuals with bleeding disorders, the condition should be managed prior to immunization to minimize the risk of bleeding. Individuals receiving long-term anticoagulation are not considered to be at higher risk of bleeding complications following immunization and may be safely immunized without discontinuation of their anticoagulation therapy.

Refer to Immunization of persons with chronic diseases for more information on the immunization of persons with bleeding disorders.

Myocarditis and/or pericarditis following vaccination

As a precautionary measure until more information is available, further doses of mRNA COVID-19 vaccines should be deferred among individuals who have experienced myocarditis and/or pericarditis within 6 weeks following a previous dose of an mRNA COVID-19 vaccine in most circumstances. This includes any person who had an abnormal cardiac investigation including ECG, elevated troponins, echocardiogram or cardiac MRI after a dose of an mRNA COVID-19 vaccine.

Those with a history compatible with pericarditis and who either had no cardiac workup or had normal cardiac investigations, can receive the next dose once they are symptom-free and at least 90 days have elapsed since vaccination.

Some individuals with confirmed myocarditis and/or pericarditis after a dose of an mRNA COVID-19 vaccine may choose to receive another dose of vaccine after discussing the risk and benefit with their healthcare provider. If another dose of vaccine is offered, it should be with a Pfizer-BioNTech Comirnaty COVID-19 KP.2 vaccine product (if 12 years of age and over) due to the lower reported rate of myocarditis and/or pericarditis following the Pfizer-BioNTech Comirnaty original (30 mcg) vaccine compared to the Moderna Spikevax original (100 mcg) vaccine among individuals 12 years of age and older. Informed consent should include discussion about the unknown risk of recurrence of myocarditis and/or pericarditis following receipt of additional doses of Pfizer-BioNTech Comirnaty vaccines in individuals with a history of confirmed myocarditis and/or pericarditis after a previous dose of mRNA COVID-19 vaccine, as well as the need to seek immediate medical assessment and care should symptoms develop.

As with mRNA vaccines, Novavax Nuvaxovid has been associated with a rare risk of myocarditis/pericarditis. No guidance is currently available regarding re-vaccination for those who experienced myocarditis/pericarditis following the Novavax Nuvaxovid COVID-19 vaccine.

Individuals who have a history of myocarditis unrelated to mRNA or protein subunit COVID-19 vaccination should consult their clinical team for individual considerations and recommendations. If the diagnosis is remote and they are no longer followed clinically for cardiac issues, they should receive the vaccine.

Guillain-Barré syndrome

Individuals with past history of GBS unrelated to COVID-19 vaccination should receive updated COVID-19 vaccines as recommended.

Individuals who developed GBS after a previous dose of a COVID-19 vaccine may receive an updated COVID-19 vaccine after consultation with their health care provider if it is determined that the benefits outweigh the risk and informed consent is provided.

Bell's palsy

Individuals should seek medical attention if they develop symptoms compatible with Bell's palsy following receipt of mRNA COVID-19 vaccines. No guidance is currently available regarding re-vaccination for those who experienced Bell's palsy after an mRNA COVID-19 vaccine. Based on the product monograph, Bell's palsy is not listed as an adverse reaction to Novavax Nuvaxovid.

Multisystem inflammatory syndrome in children or adults (MIS-C or MIS-A)

For children or adults with a previous history of MIS-C or MIS-A, vaccination or re-vaccination should be postponed until clinical recovery has been achieved or until it has been 90 days or more since diagnosis, whichever is longer.

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Other considerations

Tuberculin skin testing (TST) or interferon gamma release assay (IGRA)

There is a theoretical risk that mRNA vaccines could temporarily affect cell-mediated immunity, resulting in false-negative TST or IGRA test results. However, there is no direct evidence for this interaction. Therefore, in the absence of data and acknowledging the importance of both timely tuberculosis testing and immunization, vaccination with COVID-19 vaccines may take place at any time before, after or at the same visit as the TST or IGRA test. Repeat tuberculin skin testing or IGRA (at least 4 weeks post-COVID-19 immunization) of individuals with negative TST or IGRA results for whom there is high suspicion of latent tuberculosis infection may be considered in order to avoid missing persons with TB infection.

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Chapter revision process

This chapter was updated to reflect recent guidance on the use of COVID-19 vaccines from published NACI statements.

For supporting information on COVID-19 vaccine chapter updates, including additional references, refer to the current and/or previous summary of updates in the Canadian Immunization Guide published on the NACI webpage under COVID-19.

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Acknowledgements

This chapter revision was prepared by B Warshawsky, C Jensen, R Krishnan, J Zafack, E Wong, MI Salvadori, E Abrams, MC Tunis, S Wilson, V Dubey and R Harrison on behalf of NACI.

NACI gratefully acknowledges the contribution of: N Haddad.

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Selected references

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Footnotes

Footnote 1

Autonomous decisions should be made by Indigenous Peoples with the support of healthcare and public health partners in accordance with the United Nations Declaration on the Rights of Indigenous Peoples Act.

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