Respiratory Virus Vaccine & Treatment Recommendations 2025-2026

As the 2025-2026 respiratory season begins, Hamilton Public Health Services (HPHS) expects respiratory illness activity to increase in the coming weeks, including influenza, COVID-19, and Respiratory Syncytial Virus (RSV). Local and national surveillance shows influenza detections rising earlier than previous respiratory seasons. Further, early signals demonstrate that influenza A(H3N2) subclade K is projected to circulate during the 2025-2026 influenza season, potentially contributing to increased severity.

Early studies of vaccine effectiveness demonstrate moderate protection against H3N2. We strongly encourage vaccinating eligible individuals now - getting immunized as soon as possible gives the best protection against severe outcomes such as hospitalization and death. Healthcare providers should recommend that both staff and patients stay current with immunizations and consider antiviral treatments when appropriate for early intervention to reduce complications and improve patient outcomes. We urge you to remain vigilant and proactive in recommending immunization and antiviral use for at-risk groups to reduce the burden on healthcare systems during this season.
 

Vaccine Recommendations for Staff and Patient Populations

Further information regarding RSV prevention for infants and high-risk children can be found at: hamilton.ca/RSV

Hamilton Public Health has received its last shipment of Fluzone ® High-Dose and will not be receiving any more from the Ministry of Health for the remainder of the 2025-2026 season, as stock across the province of Ontario is depleted. Hamilton Public Health currently has a small amount available at this time, but once this inventory has been distributed, we will be substituting with Flulaval Tetra TIV or Fluzone Trivalent. Please do not delay administering flu vaccines to individuals over the age of 65 years. Hamilton Public Health, in alignment with the National Advisory Committee on Immunization (NACI), recommends the Flulaval Tetra TIV or Fluzone Trivalent as approved substitutes to the Fluzone® High-Dose TIV vaccine. In the absence of a specific product, any of the available age-appropriate influenza vaccines should be used, and vaccination should not be deferred or delayed.

Additional COVID-19 vaccine information can be found at: hamilton.ca/FallRespiratoryVaccines

Treatment Recommendations

While not a substitute for vaccination, timely treatment with antiviral medications can reduce the duration of influenza and COVID-19 symptoms and may decrease the risk of complications, including hospitalization and death. When influenza and COVID-19 are circulating in the community, antiviral treatment for high-risk priority groups should be started as soon as possible.

Ontario Health has developed a clinical resource called Recommendations for Antiviral Therapy of Seasonal Influenza, which provides guidance on the appropriate prescribing of antiviral therapy for adults and children based on the latest evidence from clinical trials. This resource includes new recommendations for the prescribing of oral Baloxavir, intravenous Zanamivir, and intravenous Peramivir, which are not included in the existing Association of Medical Microbiology and Infectious Disease (AMMI) Canada influenza treatment guidelines. The Ontario Health Influenza Clinical Guidelines and Resources website also includes helpful resources for providers about antiviral availability. For antiviral recommendations pertaining to COVID-19, refer to Ontario Health’s resource Summary of Recommendations for Drug Therapy for Adults with COVID-19 (July 29, 2025).

In congregate living settings, such as long-term care homes, early antiviral therapy is especially important to prevent severe outcomes and reduce the impact of respiratory outbreaks. Having antiviral prescriptions in advance can help prevent delays in starting therapy during potential influenza outbreaks, ensuring both staff and residents receive prompt care. Importantly, the initiation of therapy should not be delayed pending laboratory confirmation of influenza.

Reporting Requirements

To report a suspect or confirmed respiratory outbreak to HPHS, please notify the Infection Prevention and Control Program during regular business hours by calling 905-546-2063. If calling reporting after hours, on holidays, or on weekends, please call 905-546-2489 (CITY) and ask to speak with the Public Health Inspector on-call.