Is there any point in getting a flu shot that's mismatched to the virus? Here’s what the science says

Influenza is rearing its head in Canada yet again, with the number of cases starting to rise on the heels of another tough flu season in the southern hemisphere.

Scientists are particularly watching the spread of a new form of the H3N2 strain that could be mismatched to this year’s vaccine.

That notorious form of influenza A is linked to more serious disease and recently gained mutations that could make the current flu shot less effective against it, CBC News recently reported.

So is there still a point in getting a flu shot this year? Medical experts say: absolutely. The latest shot offers plenty of protection against severe illness, and is particularly important for higher-risk groups. Here’s why.

Flu vaccine effectiveness can shift each season, since the virus itself is changing constantly.

There’s also a big difference between how well flu shots protect against simply getting infected in the first place, and the level of protection against serious illness and death.

“I think for most people, they're not actually super worried about getting a sniffle or a cough. What they really want to make sure of is that they don't end up in hospital,” Matthew Miller, an immunologist and researcher at McMaster University in Hamilton, Ont., told CBC News.

In October, Miller’s latest published research — a sweeping review of hundreds of prior studies on cases of infection in adults and children following a flu shot — showed these vaccines really work in the ways that matter most.

“We found that there was a really significant reduction in disease severity, and that was really reassuring, because it provides a high degree of confidence that there's still great value in getting the vaccine,” Miller said.

Getting vaccinated can also curb virus transmission, helping stop the spread of flu to vulnerable groups such as older adults who are at a higher risk of death, noted Vancouver-based infectious disease specialist Dr. Brian Conway in a recent appearance on CBC’s Hanomansing Tonight.

Roughly nine in 10 Canadians who died of influenza and pneumonia in 2022 were aged 65 and up, Statistics Canada data shows, with more than half those deaths occurring among people aged 85 and older.

The bottom line? “You should run, not walk, and get the flu shot right now,” Conway said.

Canada’s National Advisory Committee on Immunization (NACI), made up of the country’s top vaccine advisors, says flu shots are particularly important for people at a higher risk, which can mean older adults, young children, people who are pregnant, and anyone with chronic underlying health conditions. 

“Influenza is a systemic disease,” said Conway. “You have fever, you have pains in your muscles, you have trouble getting out of bed at times, you can be short of breath. It can affect your lungs, it can lead to hospitalization, pneumonia, admission to the intensive care unit.”