Statement from the Council of Chief Medical Officers of Health (CCMOH): COVID-19 vaccination and the Omicron variant

Press Release

From: Public Health Agency of Canada


One year ago this December, the first dose of a COVID-19 vaccine was administered in Canada, marking the beginning of the largest vaccine campaign in Canadian history. Since then we have come a long way with over 80% of eligible Canadians fully vaccinated. Focus is now on offering a primary series to those aged 5 years and older, as well as adult booster doses to protect families and communities against severe COVID-19 outcomes. We know that vaccination, in combination with other public health and individual measures, works to prevent and reduce harm from SARS CoV2 and its variants.

The recent emergence and rapid transmission of the Omicron variant in Canada and across the world is a reminder that the COVID-19 pandemic is not over. Outbreaks globally can rapidly spread and lead to outbreaks in Canada. Omicron is likely to be a dominant variant circulating in the population for months to come, and it will be important to optimize protection over the longer term. Canadian and international evidence indicates that longer intervals between vaccine doses allow for a stronger immune response, and may result in better and longer lasting protection. This needs to be balanced with the rapidly escalating transmission of the Omicron variant in Canada, which has the potential to jeopardize our collective goals of minimizing serious illness and overall deaths while preserving health system capacity, and reducing transmission to protect high-risk populations.

We are still gathering information on how well vaccines work against transmission and severe disease that may result from Omicron. While data remains limited at this time, there is emerging evidence that two doses of a mRNA vaccine are less effective at preventing Omicron infection compared to previous variants but does indicate good protection against more severe disease requiring hospitalization. We also know that a booster dose is a valuable tool to offer protection from infection and do expect that a booster dose will offer very good protection against severe disease. While we do not know how long protection from boosters will last, this is an important tool at this time to help protect our collective progress against COVID-19 and preserve health care system capacity.

In this context, it is particularly important to prioritize booster doses for healthcare workers and for those at highest risk of severe illness from COVID-19. This includes those in older age groups, those living in long term care homes and other congregate living settings that provide care for seniors, Indigenous peoples and those with high risk medical conditions as identified by the National Advisory Committee on Immunization (NACI). In addition, ensuring vaccine uptake in vulnerable populations with intersecting risk factors continues to be critical. Vaccination for children 5-11 years of age is also important to help protect them from COVID-19 and to reduce disruption of school and activities that are important to their wellbeing. The interval of at least 8 weeks between doses for the pediatric primary series is about building the best immune response and protection for children over the longer term.

NACI recently reviewed its recommendations on COVID-19 vaccine adult boosters and pediatric vaccines based on evolving epidemiology and evidence on effectiveness against the Omicron variant and provided this advice to Canada’s Chief Medical Officers of Health. NACI continues to recommend the following:

  • An interval of six months or more between the final dose of a primary series and a booster dose, and an interval of at least 8 weeks between the first and second dose, including those 5-11 years of age.
  • A booster dose should be offered to older populations and those at high-risk as previously recommended (adults 50 years of age or older; adults living in long-term care homes for seniors or other congregate living setting that provide care for seniors; adults in or from First Nations, Inuit or Métis communities; recipients of a viral vector vaccine series completed with only viral vector vaccines; and adult frontline health care workers (having direct close physical contact with patients)).
  • A booster dose may be offered to those who are 18 to 49 years of age and, in light of the Omicron variant in Canada, NACI highlights that jurisdictional and individual considerations are intended to inform the need for booster doses of COVID-19 vaccine in this age range.
  • As vaccine programs roll out, booster doses should be prioritized for the groups previously listed, especially for all healthcare workers and for those at highest risk of severe illness from COVID-19.
  • For those 30 years of age and over, both Health Canada approved mRNA vaccines (Moderna Spikevax or Pfizer-BioNTech Comirnaty) may be used as the booster dose. If using Moderna, the 100 mcg dose may be preferred for those 70 years of age and over, adults who are moderately or severely immunocompromised, and residents in long-term care homes and seniors in congregate living settings.

Canada’s Chief Medical Officers of Health wish to thank NACI for their advice, which we will continue to build upon to implement strategic and effective vaccination campaigns in our jurisdictions. We remain committed to making the best use of COVID-19 vaccines based on the latest evidence and expert advice to reach our collective goals. Right now, that means increasing access to boosters to those at highest risk of severe illness from COVID-19 and to our health care providers.

We realize that managing a new variant of concern is not where we were hoping to be at the end of 2021. Individuals should continue to consider the benefits of vaccination in preventing severe illness, hospitalization and death from COVID-19. High vaccine coverage for both primary series and booster doses will help to protect the capacity of our health care system in the face of the possible impact of Omicron. Individuals should seek information from their health care provider or local public health authorities if they have questions about vaccine products that are best for them or their children.

While we are still learning about the capacity of current vaccines to protect against the Omicron variant, receiving the booster dose is expected to provide a reasonable level of protection against infection (at least in the short term) and substantial protection against severe illness. We recommend that individuals in Canada take the first booster dose offered by their local vaccine provider, as programs roll out in an accelerated manner across Canada. It remains important to continue layering other public health measures such as proper use of well-fitting masks, avoiding crowded spaces, keeping gatherings to a minimum and small, increasing ventilation and physical distancing. As we head into the holidays, we need to leverage the tools that can help us get back to enjoying the things we love most and minimize disruptions to the services and activities that are important to individuals and families. Canada’s Chief Medical Officers of Health continue to encourage all eligible individuals to get vaccinated to protect themselves and those around them.

The Council of Chief Medical Officers of Health includes the Chief Medical Officer of Health from each provincial and territorial jurisdiction, Canada’s Chief Public Health Officer, the Chief Medical Advisor of Health Canada, the Chief Medical Officer of Public Health of Indigenous Services Canada, the Chief Medical Officer from the First Nations Health Authority, and ex-officio members from other federal government departments.


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