Flu shot only 10% effective against most common strain this year

As flu season starts to move into the Atlantic region, Nova Scotia's top doctor is warning the current vaccine isn't as protective as it could be.

Dr. Robert Strang, the province's chief medical officer of health, said this year's the flu shot is only about 10 per cent effective against what is likely to become to most prevalent strain.

Nonetheless, he still advises Nova Scotians to get their flu vaccinations because "some protection is better than zero protection."

The current vaccine available throughout North America contains protection against two A strains, H3N2 and H1N1, and two B strains.

Strang said judging by what's already happened in Australia and in western Canada, it appears the H3N2 strain is going to be the most prevalent in Atlantic Canada. The problem is that's the strain against which the current vaccine offers only meagre protection.

Canadians often look to Australia for clues about what to expect.

Flu season just ended in that country, and Strang said it had a "significant amount of H3N2 flu illness." Based on the evidence, the vaccine — formulated by the World Health Organization — was only 10 per cent effective.

Regardless, Strang said it's important to get a shot.

"We may have lower effectiveness than we would like against the H3N2 strain, but some effectiveness is better than no effectiveness," he said.

According to a recent New England Journal of Medicine article, vaccine "mismatches" happen when the flu strains that are circulating change after the decision is made about the composition of that year's vaccine.

'Beef up herd immunity'

Pharmacist Curtis Chafe of the Shoppers Drug Mart on Fenwick Street in Halifax said even though the flu shot is only 10 per cent effective against this year's most common strain, he doesn't want anyone to mix up their arithmetic and think they're 90 per cent more likely to get the flu.

"Even though it may not be as strong as in previous years, that doesn't mean that you're not going to derive benefit from the flu shot," he said. "So really what it means is that more people really should be getting the flu shot."

In other words, even though the flu shot "may not be that great on an individual basis, that's when you need to beef up the herd immunity so that it works a little better," he said.

There are factors working in Nova Scotia's favour.

For example, last year the common flu strain was H3N2. Anyone who was vaccinated last year may still have some protection. Nova Scotians also have a higher rate of flu vaccination than other provinces.

Chafe said he saw a surge in visitors asking for their shot back in mid-October. Now that flu is starting to move into Nova Scotia, he expects another surge. So far this year, there have been 10 confirmed cases of the flu in the province.