Guidance on an additional COVID-19 booster dose in the spring of 2023 for individuals at high risk of severe illness due to COVID-19

On January 20, 2023, NACI published Guidance on COVID-19 vaccine booster doses: Initial considerations for 2023. This guidance consolidated and reinforced previously established booster dose recommendations and extended the fall booster program for those who had not yet received a 2022 recommended booster dose into 2023.

Since that time:

• Omicron sub-lineages continue to be the dominant strains of COVID-19 circulating in Canada. Viral sequencing is currently showing clear dominance of variants BQ.1 and BQ.1.1, while an increase in the XBB.1.5 recombinant sub-lineage is also being observed. Based on neutralization studies, BQ* and XBB* sub-lineages are more immune evasive than earlier sub-lineages (such as BA.2 and BA.5), with XBB* described as the most immune evasive sub-lineage.
• While there are fluctuations in COVID-19 transmission indicators (i.e., cases reported, hospitalizations, and deaths) and variation across provinces and territories, COVID-19 activity has been relatively stable with hospitalizations remaining at a relatively high level since the widespread circulation of Omicron in early 2022.
• Additional evidence has emerged on the performance and safety of bivalent vaccines, and the duration of protection of vaccination and hybrid immunity which help to inform the need for and benefit of additional booster doses.

NACI continues to monitor the rapidly evolving scientific data recognizing that the trajectory of the COVID-19 pandemic remains unclear. Updated recommendations will be made as needed.

NACI's recommendations remain aligned with the goals of the Canadian COVID-19 Pandemic Response that were last updated on February 14, 2022:

• To minimize serious illness and death while minimizing societal disruption as a result of the COVID-19 pandemic.
• To transition away from the crisis phase towards a more sustainable approach to long term management of COVID-19.