Data shows influenza vaccine cut risk of illness by about half, BCCDC says

Early data on the effectiveness of the flu vaccine shows it reduced the risk of illness by about half during the peak of B.C.’s season this year.

On Friday, the Canadian Sentinel Practitioner Surveillance Network released its findings on the earlier-than-usual influenza epidemic the nation has been experiencing.

“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,” said Dr. Danuta Skowronski, an epidemiologist at the B.C. Centre for Disease Control, where the SPSN is headquartered.

According to SPSN data, the majority of influenza cases this season have been linked to the H3N2 subtype of influenza A, which is often linked to more severe epidemics and lower vaccine effectiveness than other flu strains. Preliminary findings on vaccine effectiveness show this season is comparable to or higher than past ones dominated by 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.”

In a year-end interview with The Canadian Press, Dr. Teresa Tam – Canada's chief public health officer – urged Canadians to “remain vigilant” and said what happens next with COVID-19 and flu depends largely on people taking precautions for the holidays, including staying up to date with vaccinations.

The H3N2 strain that has sent many children and seniors to hospital “spiked very fast and early,” and it's possible that it could come down quickly, Tam said.

But she's watching to see if the other Influenza A strain – H1N1 – emerges, as well as Influenza B, which could come later in the flu season and “affect children in particular.”

In the most recent national FluWatch report, which covers the week of Dec. 4-10, small decreases from the previous week were noted. The rate of infection is higher than average, however, when compared to pre-pandemic levels.

That’s the same week B.C. health officials kicked off a days-long vaccine blitz in hopes of getting more people protected over the holiday season.

Everyone aged six months and older is eligible for a free flu vaccine, and can book an appointment on the B.C. government’s website through the Get Vaccinated system.