Summary of NACI rapid response of December 3, 2021: Updated recommendation on the use of authorized COVID-19 vaccines in individuals aged 12 years and older in the context of myocarditis and pericarditis reported following mRNA COVID-19 vaccination

Published: December 3, 2021

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Overview

After reviewing the latest evidence, NACI continues to:

Based on new evidence, and in order to further minimize the rare risk of adolescents and young adults experiencing myocarditis and/or pericarditis after receiving a COVID-19 mRNA vaccine, NACI now recommends:

To see the full recommendations, including the evidence and rationale behind these recommendations, please visit NACI rapid response: Updated recommendation on the use of authorized COVID-19 vaccines in individuals aged 12 years and older in the context of myocarditis and pericarditis reported following mRNA COVID-19 vaccination.

What you need to know

After reviewing the recent evidence, NACI continues to:

Strongly recommend the preferential use of a complete series of an mRNA COVID-19 vaccine over the use of a viral vector COVID-19 vaccine in all authorized age groups.

Based on new evidence, and in order to further minimize the rare risk of adolescents and young adults experiencing myocarditis and/or pericarditis after receiving a COVID-19 mRNA vaccine, NACI now recommends:

For people 12 to 29 years of age receiving an mRNA primary series:

The use of the Pfizer-BioNTech Comirnaty COVID-19 vaccine (30 mcg) is preferred over the use of the Moderna Spikevax COVID-19 vaccine (100 mcg) to start or complete a primary vaccine series. The second dose of a primary series should be provided 8 weeks after the first dose.

For people 18 to 29 years of age who are eligible to receive a booster dose of an mRNA vaccine:

The use of the Pfizer-BioNTech booster dose (30 mcg) may be preferred over the use of the Moderna booster dose (50 mcg). A booster dose should be provided at least 6 months after the completion of a primary vaccine series.

For people 30 years of age and older receiving an mRNA primary series and/or receiving an mRNA booster dose:

Either mRNA vaccine (Pfizer-BioNTech or Moderna) should be used. The second dose of a primary series should be provided 8 weeks after the first dose and a booster dose, when recommended, should be provided at least 6 months after the completion of a primary vaccine series.

To see the full rapid response, including the evidence and rationale behind these recommendations, please visit NACI rapid response: Updated recommendation on the use of authorized COVID-19 vaccines in individuals aged 12 years and older in the context of myocarditis and pericarditis reported following mRNA COVID-19 vaccination.

Quotes

"NACI has been carefully watching for rare cases of myocarditis or pericarditis following mRNA vaccination, and we have been communicating about these cases as the evidence has been emerging. We now have sufficient compelling evidence that the risks of myocarditis or pericarditis can be reduced in adolescents and young adults by choosing to provide the Pfizer-BioNTech Comirnaty vaccine, which has shown lower rates of myocarditis in those 12 to 19 years of age compared to Moderna Spikevax 100 mcg vaccine. This complements the recent NACI recommendations to provide vaccine doses at least 8 weeks apart, which is also expected to further reduce myocarditis and pericarditis risks while increasing vaccine effectiveness. For adults 30 years and older, a product preference is not necessary between the two mRNA vaccines. In some young people who are immunocompromised, the Moderna Spikevax 100mcg vaccine can be considered in consultation with their clinicians since they may have a lower immune response to COVID-19 vaccination and this vaccine may have a slightly higher vaccine effectiveness.

As a precaution, a booster dose of Pfizer-BioNTech Comirnaty may be preferred over a booster dose of Moderna Spikevax (i.e. 50 mcg dose) for adults 18 to 29 years of age who are recommended to receive a booster dose.

NACI has been able to make these recommendations because of the strong safety surveillance systems here in Canada, and also internationally, that help us refine the vaccine program over time to continually reduce very rare risks as we learn more about them. We will keep watching this space closely, and will update advice as needed."

Dr. Shelley Deeks, NACI Chair

"Based on careful review of the latest accumulated data from ongoing vaccine safety monitoring systems in Canada and internationally, this update from NACI provides further guidance to help maximize the benefits of COVID-19 vaccination while minimizing any potential risks.

NACI reaffirms that the benefits of receiving an mRNA COVID-19 vaccine continue to outweigh any potential risks of experiencing rare side effects following vaccination with an mRNA vaccine, including the rare risk of vaccine-associated myocarditis and/or pericarditis most often seen in males aged 12 to 29 years.

New Canadian and international data suggests the rare risk of myocarditis after receiving an mRNA COVID-19 vaccine may be lower with the Pfizer-BioNTech Comirnaty vaccine (30 mcg) compared to the Moderna Spikevax vaccine (100 mcg) and that a longer interval between the first and second dose in the primary series results in stronger immune response and higher vaccine effectiveness. As well, evidence suggests that longer intervals may be associated with a lower risk of myocarditis and/or pericarditis in adolescents and young adults.

Accordingly, for adolescents and adults aged 12 to 29 years, NACI preferentially recommends the use of Pfizer-BioNTech Comirnaty COVID-19 vaccine (30 mcg) over the use of the Moderna Spikevax COVID-19 vaccine (100 mcg) to start or complete a primary vaccine series. NACI further recommends that the second dose of a primary mRNA vaccine series should be provided 8 weeks after the first dose.

As always, PHAC, Health Canada and NACI will continue to monitor the safety and effectiveness of COVID-19 vaccines used in Canada and around the world and will update guidance as necessary to provide Canadians with the best possible protection."

Dr. Theresa Tam, Chief Public Health Officer of Canada

Forward agenda

NACI continues to actively review emerging evidence on COVID-19 vaccines. Upcoming recommendation may include new advice on:

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