NACI Statement on seasonal influenza vaccines for 2025–2026

The following highlights key information for immunization providers on seasonal influenza vaccine. Several influenza vaccines are authorized in Canada and the evidence on influenza immunization is continually evolving. NACI will continue to monitor the evidence and update its recommendations as needed. Refer to the remainder of the statement for details.

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. Each year, there are approximately 3 to 5 million cases of severe influenza illness and 290,000 to 650,000 deaths from influenza worldwideFootnote1.
• Most people will recover from influenza within 7 to 10 days, but some people are at greater risk of severe complications, such as pneumonia. Influenza infection can also worsen certain chronic conditions, such as cardiovascular diseaseFootnote2.
• Inactivated influenza vaccines (IIV) (which include standard dose [SD], high dose [HD], cell culture-based [cc] or adjuvanted [Adj] vaccines), recombinant influenza vaccine (RIV) and live attenuated influenza vaccine (LAIV) 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 an allergic reaction to a component 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 providers should also be aware that risks of acquiring influenza are higher in some settings and risks from influenza infection are higher in 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); and
• People whose occupational or recreational activities increase their risk of exposure to avian influenza A viruses (e.g., H5N1).

In infants less than 6 months of age, evidence is lacking to demonstrate that influenza vaccine would be effective and currently authorized influenza vaccines are not indicated for use in this age groupFootnote3. 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 pregnant women and pregnant individuals, breastfeeding women and breastfeeding individuals, 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 all eligible or 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 are available in all jurisdictions and availability of some products as part of publicly funded provincial and territorial programs may be limited or variable year to year.

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 2025–2026 influenza season. Given the global transition to trivalent influenza vaccines, the availability of various influenza vaccine preparations in Canada is evolving. Should the availability of a specific vaccine change (i.e., be made available or unavailable) after the release of this statement and prior to the 2025-2026 influenza vaccine season, NACI will communicate relevant information regarding the new vaccine preparations if required.

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.

Contraindications

For all influenza vaccines (IIV, RIV and LAIV), NACI recommends that influenza vaccination should not be given to:

• People who have had an anaphylactic reaction to a specific influenza vaccine, or to any of the components of a specific influenza vaccine, with the exception of egg;

If an individual is found to have an anaphylactic reaction to a component in 1 influenza vaccine, consideration may be given to offering another influenza vaccine that does not contain the implicated component, in consultation with an allergy specialist.

For LAIV, in addition to the above-mentioned contraindication, NACI also recommends that LAIV is contraindicated for:

• People with severe asthma (defined as currently on oral or high-dose inhaled glucocorticosteroids), active wheezing, or medically attended wheezing in the 7 days prior to the proposed date of vaccination, due to increased risk of wheezing following administration of LAIV;
  • LAIV is not contraindicated for people with a history of stable asthma or recurrent wheeze which is not active.
• Children less than 24 months of age, due to increased risk of wheezing following administration of LAIV;
• Children 2 to 17 years of age currently receiving long-term aspirin or aspirin-containing therapy, because of the association of Reye's syndrome with aspirin and wild-type influenza infection;
• Pregnant women and pregnant individuals, because it is a live attenuated vaccine and there are limited data on safety and effectiveness of LAIV in this population. There has been no identified safety signal regarding the use of LAIV in pregnancy;
• LAIV is not contraindicated in breastfeeding (lactating) individuals; however, there are limited data for the use of LAIV in this population.
  • Refer to the Updated guidance on influenza vaccination during pregnancy for additional information.
• People who are immunocompromised due to underlying disease and/or therapy; however, children living with stable HIV infection receiving antiretroviral therapy (ART) and with adequate immune function can receive LAIV.
  • Refer to the Recommendation on the use of live attenuated influenza vaccine (LAIV) in HIV infected individuals for additional information.

Precautions

• Influenza vaccination should usually be postponed in people with serious acute illnesses until their symptoms have abated;
  • More information on vaccinating individuals during acute illness can be found in the Canadian Immunization Guide's section on Contraindications and precautions associated with specific conditions: Acute Illness.
• NACI generally recommends people who have developed Guillain-Barré Syndrome (GBS) within 6 weeks of a previous influenza vaccination should not receive influenza vaccine unless another cause was found for the GBS.
  • The potential risk for a recurrent episode of GBS associated with influenza vaccination must be balanced against the risk of GBS associated with influenza infection itself and the benefits of influenza vaccination.
• For LAIV, NACI additionally recommends precautions for the following situations:
  • In the presence of significant nasal congestion or discharge that might impede delivery of LAIV to the nasopharyngeal mucosa;
  • For close contacts of people with severe immune compromising conditions; and
  • When there is administration of antivirals active against influenza (e.g., oseltamivir, zanamivir).
• Contraindications or precautions related to LAIV administration should not be used as a reason to withhold or delay immunization with an alternate vaccine. In such cases, a parenteral inactivated or recombinant influenza vaccine can be offered.

More information on contraindications and precautions can be found in the Vaccine safety and adverse events section and in the Influenza vaccine chapter of the Canadian Immunization Guide's section on contraindications and precautions.

Concurrent administration with other vaccines

Inactivated or recombinant influenza vaccines may be administered concurrently with (i.e., same day) or at any time before or after other inactivated or live attenuated vaccines.

NACI recommends that LAIV can be given together with or at any time before or after the administration of any other live attenuated or inactivated vaccine.

For information on specific concurrent administration of vaccines with influenza vaccines, refer to the Concurrent administration section of the statement.

Different injection sites and separate needles and syringes should always be used for concurrent parenteral injections. If multiple injections in the same limb are required, the injection sites should be separated by at least 2.5 cm (1 inch).

Why

• Influenza is a common vaccine-preventable disease. Vaccination is the most effective way to prevent influenza and its complications.
• Vaccination can help prevent the spread of influenza from person-to-person.
• Although most people will recover fully from influenza infection in 7 to 10 days, influenza can lead to severe disease, complications, or both, including hospitalization and death.
• Annual vaccination is required because the specific strains in the vaccine are reviewed each year by WHO and are often changed to provide a better match against the viruses expected to circulate in that given year, and the body's immune response to influenza vaccination may be transient and may not persist beyond a year.