Initial guidance on a second booster dose of COVID-19 vaccines in Canada

On April 5, 2022, the Public Health Agency of Canada (PHAC) released initial guidance on the use of second COVID-19 booster doses in Canada from the National Advisory Committee on Immunization (NACI). This guidance is based on current evidence and NACI's expert opinion.

• COVID-19 activity in Canada continues to change as public health measures are lifted and variants continue to emerge and circulate. NACI continues to emphasize the importance of completing a primary vaccine series with an authorized mRNA COVID-19 vaccine, and receiving a booster dose of an authorized mRNA COVID-19 vaccine as soon as you are recommended to do so.
• When developing initial guidance on the use of second booster doses, NACI reviewed the available evidence on how long protection from a first COVID-19 vaccine booster dose lasts and the safety and effectiveness of a second COVID-19 vaccine booster dose. NACI also considered the epidemiology of COVID-19 in Canada and risk factors associated with severe outcomes from COVID-19 (e.g., advanced age).

In the context of protection against severe disease potentially decreasing over time following the first booster dose, and/or risk of immune evasion by highly transmissible variants of concern which can cause severe disease:

• NACI recommends that jurisdictions prepare for the rapid deployment of a second COVID-19 vaccine booster dose program over the coming weeks prioritizing the following populations, as close surveillance and assessment suggest concerning trends in the COVID-19 pandemic:

(Strong NACI Recommendation)

1. Adults 80 years of age and over living in the community; and
2. Residents of long-term care or other congregate living settings for seniors. 
3. While the greatest benefit is expected in adults 80 years of age and older, jurisdictions may also consider offering a second COVID-19 booster dose to adults 70-79 years of age living in the community.

(Discretionary NACI Recommendation)

• In general, jurisdictions should aim to provide a second booster dose 6 months after the receipt of the previous booster dose, but the 6 month interval may need to be balanced with local and current epidemiology. When applicable, timing of recent COVID-19 infection should also be considered.
• A second booster dose may also be considered for adults younger than 70 years of age in or from First Nations, Métis, and Inuit communities, in collaboration with healthcare and public health partners.
• NACI is currently reviewing existing recommendations concerning first COVID-19 vaccine booster doses for younger adults (under 50 years of age) and adolescents 12 to 17 years of age, and will release a statement with updated advice in the coming weeks.