NACI Statement on seasonal influenza vaccine for 2024–2025

What

• Influenza in humans is a respiratory infection caused primarily by influenza A and B viruses. Seasonal influenza epidemics occur annually in Canada, generally in the late fall and winter months. Prior to the COVID-19 pandemic, influenza had an annual attack rate estimated at 5 to 10% in adults and 20 to 30% in children worldwideFootnote1.
• Most people will recover from influenza within a week to 10 days, but some are at greater risk of severe complications, such as pneumonia. Influenza infection can also worsen certain chronic conditions, such as cardiovascular diseaseFootnote2.
• Live attenuated influenza vaccine (LAIV), recombinant influenza vaccine (RIV) and inactivated influenza vaccines (IIV) (which include standard dose [SD], high dose [HD], cell culture-based [cc] or adjuvanted [Adj] vaccines) are all authorized for use in Canada; See Appendix A for a list of abbreviations used in this document for the different influenza vaccines.
• Influenza vaccines are the best protection against influenza and their benefits outweigh the potential risks following immunization. The safety profile of influenza vaccines has been well established. Reactions following immunization are generally benign and of short duration. Very rarely, some individuals may have allergic reactions to some components of the vaccines currently in use. Monitoring of safety signals related to influenza vaccines is ongoing.

Who

NACI makes the following recommendations for individual-level and public health program-level decision making. Individual-level recommendations are intended for people wishing to protect themselves from influenza and for vaccine providers advising individual patients about preventing influenza. Program-level recommendations are intended for provinces and territories responsible for making decisions on publicly funded immunization programs. Individual-level and program-level recommendations may differ, as the important factors to consider when recommending a vaccine for a population (e.g., population demographics, economic considerations) may be different than for an individual.

Recommendation for individual-level decision making

NACI recommends that influenza vaccine should be offered annually to anyone 6 months of age and older who does not have a contraindication to the vaccine. Patients and health care providers should also be aware that risks are higher in some settings and for some individuals than others. Immunization is particularly important for the following groups (see List 1):

• People at high risk of severe disease, influenza-related complications, or hospitalization
• People capable of transmitting influenza to those at high risk
• People who provide essential community services (including health care workers)
• People in direct contact with poultry infected with avian influenza during culling operationsFootnote3.

In infants less than 6 months of age, evidence is lacking to demonstrate that influenza vaccine would be effectiveFootnote3. Currently, authorized influenza vaccines are not indicated for use in infants less than 6 months of age. For these reasons, NACI recommends that influenza vaccine should not be offered to these infants. Since infants less than 6 months of age are at high risk of influenza-related illness, the influenza vaccine should be offered to individuals who are pregnant, breastfeeding, and any household contacts and care providers of young infants.

Recommendation for public health program-level decision-making

The national goal of the annual influenza immunization programs in Canada is to prevent serious illness caused by influenza and its complications, including death. Programmatic decisions to provide influenza vaccination to target populations as part of publicly funded provincial and territorial programs depend on many factors, such as cost-effectiveness evaluation and other programmatic and operational factors.

NACI recommends that influenza vaccine should be offered as a priority to the groups for whom influenza vaccination is particularly important.

How

The benefits and risks of influenza vaccination should be discussed prior to vaccination, including the risks of not being immunized.

Choice of influenza vaccine

A variety of influenza vaccines are authorized for use in Canada, some of which are authorized for use only in specific age groups. Furthermore, not all products will necessarily be made available in all jurisdictions and availability of some products as part of publicly funded provincial and territorial programs may be limited.

Dose and route of administration

The dose and route of administration vary by influenza vaccine product.

See Appendix B for information on characteristics of all influenza vaccines expected to be available for use in Canada for the 2024–2025 influenza season.

Schedule

NACI recommends that:

• Adults and children 9 years of age and older should receive 1 dose of influenza vaccine each year; and
• Children 6 months to less than 9 years of age who have never received the seasonal influenza vaccine in a previous influenza season should be given 2 doses of influenza vaccine in the current season, with a minimum interval of 4 weeks between doses.
• Children 6 months to less than 9 years of age who have been vaccinated with 1 or more doses of seasonal influenza vaccine in any previous season should receive 1 dose of influenza vaccine per season thereafter.