Archived 14: Summary of National Advisory Committee on Immunization statement of June 17, 2021

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This is an archived version. Please refer to current COVID-19 vaccine pages:

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COVID-19 vaccine schedules

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

Second doses: What you need to know

Other updates

Myocarditis and pericarditis

Simultaneous administration of 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:

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