Newspaper article The Canadian Press

Don't Give Flu Shot a Miss This Season Based on Last Year's Failure, Doctors Say

Newspaper article The Canadian Press

Don't Give Flu Shot a Miss This Season Based on Last Year's Failure, Doctors Say

Article excerpt

Last year's flu shot failure an anomaly, MDs say

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TORONTO - It's that time of year again, time for Canadians to think about getting that jab in the arm to protect themselves against the dreaded winter scourge -- the flu.

And while the makeup of last year's influenza vaccine missed the mark when it came to effectiveness, infectious disease experts say people shouldn't shy away from this season's shot based on that failure.

"It's important to know that last year doesn't predict this year," says Dr. Bryna Warshawsky of Public Health Ontario. "And last year was an anomaly in terms of past years."

Each February, the World Health Organization chooses which influenza strains should be included in the coming fall's vaccine, based on those circulating at the time.

That best-guess choice has to be made early because it takes six months for manufacturers to produce the vaccine and stockpile enough doses to supply provincial and territorial inoculation programs, which typically begin in mid to late October.

Cases of influenza -- a disease that for many people means a miserable week of coughing, sneezing, body aches and fever -- usually start being reported in late November to early December and often continue into early spring.

On average, an estimated 12,500 Canadians are admitted to hospital each year for complications arising from the flu and about 3,500 die, according to the Public Health Agency of Canada.

There are three types of influenza viruses: A, B and C. Human influenza A and B viruses cause seasonal epidemics in North America almost every winter, says the U.S. Centers for Disease Control.

Traditional seasonal flu shots -- known as trivalent vaccines --are configured to protect against two A strains, H3N2 and H1N1, and one of two B-lineage influenza viruses.

"But in that six months between when the vaccine choices are made and the vaccine actually gets delivered, the virus continues to change and sometimes it changes to an extent that it doesn't match what was selected in February," says Warshawsky.

"Last year, the problem was the H3N2."

The bug had mutated, making it genetically dissimilar enough to the H3N2 component in the vaccine to offer virtually no protection against the respiratory infection -- especially since the dominant strain making people sick just happened to be H3N2.

"Ideally what we would like is that the influenza strain included in the vaccine is the identical twin of what is circulating out in the community," explains Dr. Danuta Skowronski, an expert in influenza and emerging respiratory pathogens at the B.C. Centre for Disease Control in Vancouver.

That seldom happens because of the lead time needed for the manufacturing process, she says.

"So typically what we're aiming for is that these viruses might be considered like siblings -- brothers or sisters -- in terms of the similarities between them. …

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