Summary of NACI statement of April 5, 2022: Initial guidance on a second booster dose of COVID-19 vaccines in Canada

Published: April 5, 2022

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Organization:Public Health Agency of Canada

Published: 2022-04-05

Overview

  • 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:
    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.
  • 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.

For the full statement, including supporting evidence and rationale, please see NACI Statement: Initial guidance on a second booster dose of COVID-19 vaccines in Canada.

For more information on NACI's recommendations on the use of COVID-19 vaccines, please refer to the COVID-19 vaccine chapter in the Canadian Immunization Guide (CIG), as well as additional statements on the NACI web page.

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.

What you need to know

  • On April 5, 2022, the Public Health Agency of Canada (PHAC) released initial guidance from the National Advisory Committee on Immunization (NACI) on the use of second booster doses of COVID-19 vaccines in Canada. This guidance is based on current evidence and NACI's expert opinion.
  • COVID-19 epidemiological indicators vary across Canada, with some areas seeing an increase in COVID-19 activity. An increase in COVID-19 activity is expected as public health measures are lifted and the highly transmissible Omicron BA.2 variant spreads.
  • NACI's recommendations on the use of second COVID-19 booster doses are based on evidence on the need for (e.g., decrease of vaccine effectiveness over time), and benefit of (safety and effectiveness) a second booster dose in the Canadian context.
  • Evidence shows that protection against severe disease and hospitalization due to COVID-19 is higher in people who have received a first booster dose compared to those who have only received a primary series. There is limited evidence on how long protection from a first booster dose persists, with studies suggesting some decrease over time.
  • Some jurisdictions have already offered a second booster dose to specific high-risk groups, including long-term care home residents. Preliminary data indicate that a second booster dose provides additional protection, including against severe disease.
  • Preliminary data suggest the safety of a second booster dose of an mRNA COVID-19 vaccine is similar to previous doses. Canadian and international safety data suggest a second booster dose is well tolerated with no additional safety signals.
  • NACI recommends the prioritization of adults 80 years of age and older living in the community and residents of long-term care or other congregate living settings for seniors because they are at higher risk of experiencing severe outcomes from COVID-19.
  • Second booster dose immunization programs for other high-risk groups and the general public may be needed in the future if data suggest concerning trends in COVID-19 pandemic.
  • Provinces and territories may refer to NACI's full statement for vaccine options and factors to consider when determining the need for, and benefit of, future booster dose programs in various populations.
  • At this time, recommendations for second COVID-19 vaccine booster doses are off-label, as second booster doses are not currently authorized for use by Health Canada.
  • NACI will continue to monitor the emerging evidence on the need for, and benefit of, second COVID-19 vaccine booster doses and will update guidance as needed.

For the full statement, including supporting evidence and rationale, please see the NACI Statement: Initial guidance on a second booster dose of COVID-19 vaccines in Canada.

For more information on NACI's recommendations on the use of COVID-19 vaccines, please refer to the COVID-19 vaccine chapter in the Canadian Immunization Guide (CIG), as well as additional statements on the NACI web page.

Quotes

"NACI has reviewed the latest evidence on second COVID-19 booster doses in older adults. In older adults, these additional boosters can provide increased protection against severe disease from COVID-19 as the first booster dose protection wanes, and as the BA.2 variant of concern spreads. It may be necessary for provinces and territories to consider using second boosters in some settings as close surveillance and assessment suggests concerning trends in the trajectory of the pandemic due to the lifting of public health measures and as the highly transmissible Omicron BA.2 variant of concern circulates. While the greatest benefit of second boosters are expected in long-term care, congregate living settings for seniors, and for those 80 years of age and older living in the community; jurisdictions may also choose to offer a second COVID-19 booster dose to adults 70 to 79 years of age living in the community.

As we move through the spring and summer months, NACI will continue reviewing emerging booster evidence and jurisdictions will be watching the epidemiology closely. Broad deployment of a second booster dose to the general population is not necessary at this time to support the core program goal of preventing severe disease. However, future planning should take into account that additional boosters may be required in the fall of 2022 or earlier in other groups if close monitoring suggests more concerning trends in the COVID-19 pandemic."

Dr. Robyn Harrison, NACI Vice-chair

"COVID-19 disease activity continues to be reported across Canada, with some areas reporting recent increased transmission following the easing of public health measures. As the SARS-CoV-2 virus continues to circulate and evolve, we need to think ahead and be prepared for potential new variants of concern and/or future waves of the pandemic.

NACI's initial guidance on the use of second booster doses of COVID-19 vaccines will help provinces and territories decide on timing and prioritization for rollout of these immunization programs across different populations, based on local epidemiology and unique circumstances in their regions. Preliminary data indicate that a second booster dose of a COVID-19 vaccine can offer additional protection against infection, severe illness, hospitalization and death. At this time, we expect specific high-risk groups, including residents of long-term care homes and seniors aged 80 years or over living in the community, to benefit the most from a second booster dose. As NACI's review continues, the recommendation stands for adults to receive a COVID-19 primary vaccine series and a first booster dose of an authorized mRNA vaccine. Keeping COVID-19 vaccinations up-to-date is one of the best ways to protect ourselves and our communities against COVID-19 and to collectively reduce the impact of future waves. I thank NACI for continuing to provide timely, expert advice to help protect the health of Canadians."

Dr. Theresa Tam, Chief Public Health Officer
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