Flu vaccine only 23% effective in U.S., even less effective in Canada

CBC News: January 15, 2015

The flu vaccine seems effective in reducing the risk of flu by 23 per cent, based on an early estimate from the U.S. among people going to the doctor for respiratory illness.

Canadian and U.S. health officials have said the most common type of flu circulating this season is H3N2, which is not well-matched with the seasonal flu vaccine.

On Thursday, the U.S. Centers for Disease Control and Prevention released an estimate based on 2,321 American children and adults who got the flu vaccine between November and January. The CDC said vaccinated people had a 23 per cent lower chance of winding up at the doctor with the flu.

The poor effectiveness likely reflects the fact that more than two-thirds of circulating flu viruses are genetically different or “drifted” from seasonal flu vaccines, the CDC said in its Morbidity and Mortality Weekly Report.

The effectiveness was highest among children aged six months to 17 at 26 per cent. Effectiveness fell to about 12 per cent among people aged 18 to 49 and 14 per cent for those aged 50 and older.

In Canada, the flu vaccine could be working even more poorly, with “little or no protection.”

“About 98 per cent of the viruses are mismatched that have been characterized in Canada, whereas in the U.S. its closer to about 68 per cent, or about two-thirds are mismatched. So it’s not a good omen,” said Dr. Danuta Skowronski of the British Columbia Centre for Disease Control.

(read the full article at CBC)

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