Archived 16: Summary of National Advisory Committee on Immunization (NACI) updates of July 22, 2021

Recommendation for people previously infected with SARS-CoV-2 virus

On this page

• Overview
• What you need to know
• Quotes

Overview

• On July 22, 2021, the Public Health Agency of Canada released updated advice from the National Advisory Committee on Immunization (NACI) on the use of COVID-19 vaccines in people previously infected with the SARS-CoV-2 virus. These recommendations are based on current scientific evidence and NACI's expert opinion.

NACI continues to recommend:

• A complete series of a COVID-19 vaccine may be offered to individuals who have had confirmed SARS-CoV-2 infection.

To see the full update, please visit NACI Recommendations on the use of COVID-19 vaccines.

What you need to know

• When making this recommendation, NACI reviewed data from real world studies on:
  • the protective immune response previous SARS-CoV-2 infection offers against re-infection;
  • immune responses after one and two doses of a COVID-19 vaccine in people with a history of SARS-CoV-2 infection; and
  • the safety of offering two doses of a COVID-19 vaccine to people with a history of SARS-CoV-2 infection.
• In the absence of evidence on long-term one-dose vaccine effectiveness in people who were previously infected with the SARS-CoV-2 virus, particularly in relation to variants of concern, NACI continues to recommend that these individuals may be offered a complete COVID-19 vaccine series.
• The risk of re-infection in people who had a SARS-CoV-2 infection before appears to be low. People who do become infected again often have no symptoms.
• Studies suggest the rate of re-infection in people with a history of SARS-CoV-2 infection who have not been vaccinated is similar to the rate of first infection in people who have received two doses of an mRNA vaccine.
• Previous infection with the SARS-CoV-2 virus may provide protection against re-infection for six months or longer; however, the risk of re-infection with a variant is not clear at this time.
• As of late June 2021, four variants of concern B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta) have been detected in Canada to date. They account for an estimated 70% of recently reported cases, most of which are either B.1.617.2 (Delta) or B.1.1.7 (Alpha) variant).
• Current evidence shows the immune response in individuals with a history of SARS-CoV-2 after one dose of a COVID-19 vaccine is similar to the immune response seen in individuals without a history of infection after two doses of a COVID-19 vaccine.
• Individuals should wait to receive a vaccine until they no longer have acute symptoms of COVID-19 and are no longer infectious to others. Other factors, like the level of SARS-CoV-2 transmission in the community, the circulation of variants and an individual's risk of exposure to the virus and severe COVID-19 disease, should also be considered when deciding when to vaccinate.
• Provinces and territories consider NACI advice when designing and delivering their immunization programs. It is up to provinces and territories to determine the best approach based on their unique circumstances.
• Individuals with a history of SARS-CoV-2 infection may decide to complete their vaccine series in order to meet vaccination-related requirements to participate in activities that require proof of full vaccination.
• NACI will continue to monitor the evolving evidence on vaccination in those with a history of SARS-CoV-2 infection and will update recommendations as needed.

Quotes

"We continue to learn more about infection from SARS-CoV-2 virus and its variants, and how our bodies are responding to COVID-19 vaccines. The latest evidence and our understanding of immunology tells us that individuals who have been previously infected have adequate protection for several months after the infection, which is improved after the first dose of COVID-19 vaccine. We are not clear how this protection will translate against new variants of the virus. There are many reasons that jurisdictions may offer, and individuals may choose, a complete series of two vaccines even after a previous infection, including participation in activities or travel."

Dr. Shelley Deeks, NACI Chair

"I would like to thank the experts on NACI for their careful and thoughtful review. As we continue to study and learn about SARS-CoV-2 and the human response to this virus, recommendations will be tailored and updated. At this point, those who have been previously infected do have an immune response that is enhanced by one or two doses of the vaccine. Provinces and territories will consider NACI advice in the design of their programs. Vaccines, in combination with public health measures and individual precautions, continue to be key in reducing the spread of COVID-19."

Dr. Theresa Tam, Chief Public Health Officer