Preliminary findings show the vaccine has cut the risk of influenza illness by about half during this season’s early and ongoing influenza A epidemic. 

“The earlier-than-usual influenza epidemic this season has enabled us to assess vaccine effectiveness earlier than usual,” said Dr. Danuta Skowronski, physician epidemiologist at the BC Centre for Disease Control (BCCDC) and lead of the Canadian Sentinel Practitioner Surveillance Network (SPSN). “We will update our analyses in the new year, but these interim findings show a substantial reduction in the risk of influenza illness for vaccinated people who seek medical care.” 

The early findings come from the SPSN. Headquartered at the BCCDC, the SPSN includes hundreds of primary care providers within the four largest provinces of Canada: Alberta, British Columbia, Ontario and Quebec. For more than a decade, the SPSN has provided mid-season influenza vaccine effectiveness estimates, typically in January or February, based upon specimens and data collected from patients seeking care for flu-like illness. 

“Vaccine protection is especially important for people at higher risk of severe complications and for a health care system that is managing the circulation of multiple respiratory viruses at the same time as we enter the holiday period.” 

 

In B.C. and across Canada, the majority of influenza cases this season have been due to the H3N2 subtype of influenza A. The H3N2 subtype is often associated with more severe epidemics and with lower vaccine effectiveness than for other kinds of influenza A or B. The SPSN vaccine effectiveness estimate this season is comparable or higher than measured in previous seasons against the H3N2 subtype.

“Vaccination ahead of the epidemic peak provides the most benefit,” said Skowronski. “Although surveillance data suggest we are currently on the downslope of the epidemic curve, the virus will continue to circulate for several weeks, with the possibility of more spread during the holiday period. A secondary wave due to influenza B also sometimes follows later in the season. If you have not yet been vaccinated against influenza, now is the time.” 

“Vaccines are available for everyone six months and older in B.C. and these preliminary findings show how vaccination remains our best defence against respiratory illnesses. By getting vaccinated against influenza, you can help protect our public health system and the young children and elderly people around you,” said Adrian Dix, B.C. Minister of Health.

 

Take prevention measures during respiratory season: