As H3N2 spreads, can you still get your flu shot before holiday gatherings?

As Canadians gather for the holidays this week, a new strain of influenza is threatening to play spoilsport. But experts say there are still many ways you can protect yourself and your loved ones from H3N2 and its new subclade K strain.

The rate of hospitalization from influenza in Canada has nearly doubled compared to the previous week of available data, with infections now up almost 30 per cent, Health Canada’s latest figures show.

For the week ending Dec. 13, Canada saw 11,646 new cases of flu being detected, which means 27.7 per cent of all the tests conducted in the country came out positive.

“It’s not too late to get a flu shot this year,” said Dr. Isaac Bogoch, infectious disease specialist at Toronto General Hospital.

A mutation in the new strain may be allowing the virus to slip past our defences in some cases, said Dr. Fahad Razak, internal medicine physician at St. Michael’s Hospital and professor at the University of Toronto.

“Our vaccines do protect against it, but over the course of the summer, there was some additional mutations in one of the branches of this version called subclade K. And those mutations probably are allowing the virus to have some ability to evade our immune protections,” Razak said.

Despite the mutations, however, the vaccine remains your best bet against the virus, he said.

The United Kingdom is ahead of Canada in the flu season and may give a good indication to how the virus is responding to vaccines, Razak said.

“The best available evidence that we have this year does show that the vaccine remains very protective against severe disease — (including) ending up in hospital, ending up at the intensive care unit or even dying,” he said.

The flu shot has been 72 to 75 per cent effective at preventing emergency department visits in children in the U.K. due to H3N2, and 32 to 39 per cent effective in adults, according to data published in Eurosurveillance, one of Europe’s top journals on infectious diseases.

The dominant strain right now is H3N2, a variant of influenza A, but epidemiologists warn of a second potential wave of influenza B strains later in the spring, Razak said.

“Some years, we have a second surge that happens a little bit later in the year, into the spring. That tends to be the other form of influenza, which is influenza B, and this vaccine also protects against that,” he said.

Getting the vaccine does not guarantee that someone won’t get sick, but the flu is likely to be “relatively mild” and “more like the common cold” for vaccinated individuals, Razak said.

“You don’t feel well, maybe you stay home for a day or two, but then you move on with your life,” he said.

He said Canadians should think of getting their flu shot like they think of putting on their seat belt while driving — it should be a no-brainer.

“Does it absolutely prevent you from dying in a car accident? Of course not. But does it greatly reduce the risk of a serious injury? It does,” he said.

While it would take around two weeks for the vaccine to get you to the full level of protection, any protection is better than not being vaccinated at all, Razak said.

“If you don’t have two weeks, that’s OK. If you get vaccinated today and you get exposed to someone around New Year’s Eve at a social event, you’re much more protected than you are if you weren’t vaccinated,” he said.

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As multi-generational families gather around the holidays, Bogoch said it is important tor remember who the most vulnerable people are.

“You want to see who’s at greatest risk for emergency department visits and hospitalizations. It’s the youngest cohorts, the oldest cohorts, pregnant women and people with underlying health conditions, like structural heart or lung disease or immunocompromised states,” Bogoch said.

“If you’re sick, don’t go. Stay home. No point getting everyone else sick,” he added.

The youngest and oldest Canadians are getting hit the hardest. The highest rate of weekly hospitalizations was in adults aged 65 years and over and children aged four years and younger.

Health Canada data showed that 44 per cent of the new cases detected were in those aged 19 years or younger.

“All of the lessons from COVID in terms of the general strategies apply to the flu as well,” Razak said.

“If you are at a workplace where you can work from home or take a day or two off, don’t go in and get your co-worker sick. If there’s a family gathering and you have elderly high-risk people around and you are very infectious, you’re coughing, you have a fever and you avoid going, you’re going to do everyone else there a favour,” he said.

“We’re well beyond the era of mask mandates, but you can put on a mask and it’s going to reduce your risk of getting an infection. Simple things that we all know. Wash your hands,” Bogoch said.

Older Canadians can also get a higher-dose version of the flu vaccine, which is available across most of the country, Razak said.

Masking in public, washing your hands and getting vaccinated all form different layers of protection from influenza.

“You put them all together, your chance of getting really sick this season will go down dramatically,” Razak said.