On October 7, 2022, Health Canada authorized the use of the Pfizer-BioNTech Comirnaty BA.4/5 Bivalent (30 mcg) COVID-19 vaccine as a booster dose in individuals ≥12 years of age. The Pfizer-BioNTech Comirnaty BA.4/5 Bivalent (30 mcg) COVID-19 vaccine is the second bivalent Omicron-containing mRNA COVID-19 vaccine authorized for use in Canada.

The epidemiology of COVID-19 continues to change and there is still considerable uncertainty regarding the likelihood, timing, and severity of potential future COVID-19 waves. It is possible that, consistent with other respiratory viruses, the incidence of COVID-19 may increase in late fall and winter and/or that new variants of concern (VOCs) may emerge.

Although Omicron and its sublineages have largely been associated with less severe illness compared to previous VOCs, the severity of Omicron sublineages BA.4 and BA.5 in comparison to other Omicron sublineages is currently unclear, and data are still emerging at this time (1-3) .

The Omicron variant has demonstrated partial evasion of immunity conferred by the original COVID-19 vaccines or by a previous infection with a SARS-CoV-2 variant that emerged prior to Omicron. The immune evasion exhibited by Omicron sublineages BA.4 and BA.5 may be greater than that exhibited by previous Omicron sublineages, although evidence is still emerging at this time.

While the proportion of Canadians vaccinated with a primary series is high, the proportion who have received at least one additional dose has plateaued at a much lower level.

NACI continues to strongly recommend a primary series with an original mRNA vaccine in all individuals 5 years of age and up, and that children 6 months to 4 years of age may receive a primary series with an original mRNA vaccine. NACI has also previously provided recommendations for a booster dose with an authorized COVID-19 vaccine for all adults, adolescents, and children 5-11 years of age. Immunization of those who are eligible for vaccination but have not yet received their recommended doses (primary series or booster) remains a top priority in Canada. As with previous COVID-19 booster programs, a fall booster dose will be most important for older adults (i.e., ≥65 years of age) and other populations at increased risk of severe COVID-19 disease (e.g., individuals with immunocompromising conditions).

  • Recommendation
  • Americas
  • Canada
  • booster dose
  • COVID-19