Canadian study shows flu vaccine halves risk of infection this year

Associated Press

TORONTO - New data suggest that Canadians who got a flu shot this year cut their risk of getting sick enough to require medical care by about half.

That's slightly lower than the vaccine effectiveness estimate that the U.S. Centers for Disease Control released late last week.

In the U.S., the CDC said this year's flu vaccine reduces the risk by 62 per cent overall, and by 55 per cent against influenza A viruses,

Dr. Danuta Skowronski, who led the Canadian study, says the cross-border difference relates to the fact that in Canada, most infections this year are caused by the influenza A subtype H3N2.

Skowronski, who is with the British Columbia Centre for Disease Control, says while the protection isn't as high as public health would like, it's still significant.

The Canadian estimate is based on data submitted by a network of several hundred family doctors in Quebec, Ontario, Manitoba, Alberta and British Columbia.

The U.S. overall figure was brought up by the fact that the vaccine effectiveness estimate for the influenza B component of the vaccine was 70 per cent.

But in Canada the surveillance network hasn't seen enough influenza B cases to generate a reliable effectiveness estimate for it yet.

Skowronski says an additional analysis will be generated at the end of the flu season.

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