Archived 14: Summary of National Advisory Committee on Immunization statement of June 17, 2021
Notice to reader
This is an archived version. Please refer to the most current version of the recommendations on the use of COVID-19 vaccines.
On this page
- COVID-19 vaccine schedules
- First doses: What you need to know
- Second doses: What you need to know
- Other updates
- NACI forward agenda
COVID-19 vaccine schedules
- On June 17, 2021, the Public Health Agency of Canada released updated recommendations from the National Advisory Committee on Immunization (NACI) on first and second doses of COVID-19 vaccines authorized for use in Canada. These updates are based on current scientific evidence and NACI expert opinion.
- NACI reviews new scientific evidence on COVID-19 vaccines on an ongoing basis and revises its guidance on the use of authorized vaccines accordingly. Due to the rapid emergence of new evidence, NACI issues updates to its guidance regularly.
- In making its recommendations, NACI considered:
- The increasing availability of mRNA vaccines (Pfizer-BioNTech, Moderna) in Canada;
- Emerging evidence suggesting better immune responses when a first dose of the AstraZeneca vaccine is followed by a second dose of the Pfizer-BioNTech mRNA vaccine;
- The risk of Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT) associated with viral vector vaccines (AstraZeneca, Janssen) but not associated with mRNA vaccines (Pfizer-BioNTech, Moderna); and
- Principles of ethics, equity, feasibility, and acceptability.
- For first doses, NACI recommends that:
- An mRNA vaccine (Pfizer-BioNTech, Moderna) is preferred to start a vaccine series, unless there is a contraindication, for example, because of an allergy to an mRNA vaccine or its components.
- A viral vector vaccine (AstraZeneca, Janssen) may be offered to start a vaccine series when an mRNA vaccine is inaccessible or contraindicated, for example, because of an allergy to an mRNA vaccine or its components.
- NACI's previous recommendation - that people who wanted earlier vaccination could receive a viral vector vaccine rather than wait for an mRNA vaccine - reflected the limited supply of mRNA vaccines at the time and the imperative of protecting vulnerable populations from serious illness and death from COVID-19.
- For second doses, NACI recommends that:
- Individuals who received a first dose of an mRNA vaccine (Pfizer-BioNTech, Moderna) should be offered the same mRNA product for their second dose. If the same product is not readily available, or the product used for the first dose is unknown, another mRNA vaccine is considered interchangeable and should be used to complete the series.
- An mRNA vaccine is now preferred as the second dose for individuals who received a first dose of the AstraZeneca/COVISHIELD vaccine, based on emerging evidence of a potentially better immune response from this mixed vaccine schedule and to mitigate the potential risk of VITT associated with viral vector vaccines.
- People who received two doses of AstraZeneca/COVISHIELD vaccine can rest assured that the vaccine provides good protection against infection and very good protection against severe disease and hospitalization.
Receiving a second vaccine dose for a two-dose schedule is essential to provide better and longer-term protection against COVID-19 for individuals and for the entire community.
NACI continues to closely monitor the evolving evidence on COVID-19 vaccines and will update recommendations as needed. To see the full statement, please visit Recommendations on the use of COVID-19 vaccines.
First doses: What you need to know
- NACI previously recommended that people who wanted earlier vaccination could receive a viral vector vaccine (AstraZeneca/COVISHIELD, Janssen) rather than wait for an mRNA vaccine (Pfizer-BioNTech, Moderna) if certain conditions were met.
- This recommendation was based on a public health benefit-risk analysis comparing the rates of VITT and the risk of COVID-19 while waiting for an mRNA vaccine.
- NACI now recommends that an mRNA vaccine is preferred as a first dose unless an mRNA vaccine is inaccessible or there is a contraindication, for example, an allergy to an mRNA vaccine or its components.
- NACI recommends a viral vector vaccine may be offered to individuals in the authorized age group when an mRNA vaccine is inaccessible or contraindicated, for example because of an allergy to an mRNA vaccine or its components.
- In making this recommendation, NACI considered the recent epidemiology of COVID-19 in Canada, including the circulation of variants of concern; evidence on VITT, including risk and rates, associated with viral vector vaccines but not associated with the mRNA vaccines; Canada's increasing supply of mRNA vaccines; and a comprehensive analysis of the implications on ethics, equity, feasibility, and acceptability. Please see the full statement for the evidence and rationale for this recommendation.
- If you received a COVID-19 vaccine, you made the right choice. You chose to protect yourself, your family and your community from COVID-19.
Second doses: What you need to know
- Second doses are important to provide better and longer-term protection against COVID-19 for individuals and for the entire community. A different vaccine product may be offered for a second dose, which is known as vaccine interchangeability or a 'mixed vaccine schedule'.
- Emerging evidence from studies in Germany suggests a potentially better immune response, including against variants of concern, when a first dose of the AstraZeneca vaccine is followed by a second dose of the Pfizer-BioNTech mRNA vaccine, compared to two doses of the AstraZeneca vaccine. Evidence continues to suggest a first dose of the AstraZeneca vaccine followed by a second dose of the Pfizer-BioNTech mRNA vaccine has a good safety profile.
- As such, NACI recommends that an mRNA COVID-19 vaccine is now preferred as the second dose for individuals who received a first dose of the AstraZeneca/COVISHIELD vaccine.
- Receiving an mRNA vaccine as a second dose also mitigates the rare risk of VITT that is associated with viral vector vaccines. The rate of VITT after the second dose of the AstraZeneca/COVISHIELD vaccine appears to be lower than with the first dose but has increased over time, with current estimates of approximately 1 per 600,000 people vaccinated. Individuals should consider talking to a health care professional to help understand the best option for their situation.
- Getting two doses of the AstraZeneca/COVISHIELD vaccine provides good protection against COVID-19 disease. Receiving a full series of a COVID-19 vaccine helps protect you, your family and your community against COVID-19.
Myocarditis and pericarditis
- Rare cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the heart lining) following vaccination with mRNA COVID-19 vaccines have been reported in Canada and internationally, including in Israel and the United States.
- No clear association between myocarditis/pericarditis and mRNA COVID-19 vaccines has been established in Canada. This may change as more evidence emerges and Canada administers more second doses of mRNA vaccines.
- Most international cases have occurred after a second dose of an mRNA vaccine in males younger than 30 years. Cases have generally been mild and resolved with medical treatment. There are no data yet on myocarditis/pericarditis using a mixed vaccine schedule.
- NACI is not making any changes to recommendations based on these reports at this time. The Public Health Agency of Canada, Health Canada and NACI continue to closely monitor this situation and will take appropriate action if needed.
Simultaneous administration of vaccines
- As a precaution, NACI continues to recommend that COVID-19 vaccines and non-COVID-19 vaccines should not be routinely given at the same time.
- If possible, COVID-19 vaccines should be given at least 14 days after and 28 days before other vaccines, with some exceptions. This will help to avoid possible overlapping side effects and potential (but unknown) interference with the immune response between vaccines.
- There may be circumstances when a dose of a COVID-19 vaccine and a non-COVID-19 vaccine need to be administered at the same time or when a non-COVID-19 vaccine needs to be administered within 28 days after a COVID-19 vaccine. Examples include when a non-COVID-19 vaccine is needed after an exposure to another infectious disease or when an individual is about to start a treatment that will weaken their immune system.
- A healthcare professional can help to make this assessment and can discuss the benefits and possible risks with the individual.
- To see the full statement, please visit Recommendations on the use of COVID-19 vaccines.
"With mRNA vaccine supply in Canada continuing to increase and the ongoing risk of the rare but serious adverse event called VITT that is associated with the viral vector vaccines after first and second doses, NACI now recommends that an mRNA vaccine is the preferred choice for starting a COVID-19 vaccine series."
"NACI is also recommending that for anyone who received a first dose of AstraZeneca/COVISHIELD, an mRNA vaccine is now preferred for the second dose. Since NACI first looked at mixed vaccine schedules, new evidence is starting to emerge suggesting immune responses are better when a first dose of the AstraZeneca vaccine is followed by an mRNA vaccine as a second dose. NACI understands individuals may feel uncomfortable following a mixed vaccine schedule and suggests speaking with a health care professional about the decision on which vaccine product to receive for their second dose."
"Anyone who has already received two doses of AstraZeneca/COVISHIELD can rest assured that they are protected, particularly against severe illness. There is no need for a third dose at this time."
Dr. Shelley Deeks, NACI Chair
"NACI's independent guidance on the use of authorized COVID-19 vaccines is invaluable to Canada's pandemic response. The evolution of its recommendations, based on rapidly emerging scientific evidence, provides public health authorities with sound advice to help protect the health and well-being of Canadians. Because of the international research effort, we are learning more about COVID-19 every day. The experts on NACI are continuously analyzing complex data and scientific information and applying their expertise to guide us in the optimal use of COVID-19 vaccines."
Dr. Theresa Tam, Chief Public Health Officer of Canada
NACI forward agenda
NACI continues to actively review emerging evidence on COVID-19 vaccines. Upcoming recommendations may include new advice on:
- Recommendation on the use of the Moderna COVID-19 mRNA vaccine in adolescents (pending a regulatory decision by Health Canada)
- Optimal number of doses for people who have been previously infected with SARS-CoV-2 (expected in summer 2021)
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