Flu vaccine production issue may be behind last year’s modest protection: study

TORONTO – Studies showed flu vaccine offered only modest protection in the winter of 2012-2013, which was a harsh season for influenza.

Now new Canadian research is offering an explanation for why the vaccine offered less than optimal protection last winter.

The scientists say that mutations that occurred in the process of making the vaccine actually pushed it off target for the flu shot’s H3N2 component.

H3N2 viruses were responsible for most of the influenza activity recorded last winter; that family of viruses causes severe illness in the elderly.

The researchers say that the H3N2 strain that the World Health Organization selected for the 2012-2013 vaccine was a good match for the viruses that circulated that winter.

But the adapted virus that ended up being used for vaccine production worldwide had mutations that made it less effective against those circulating viruses.

The mismatch between the vaccine virus and the circulating viruses wouldn’t have caused big problems in North America this winter, because almost all of the flu activity here this year was caused by the H1N1 strain.

But the same H3N2 virus has been selected for next winter’s flu vaccine, suggesting there may be a problem ahead if H3N2 viruses play a big role next flu season.

The study is published in the journal PLoS One. The lead author is Dr. Danuta Skowronski, an influenza expert at the British Columbia Centre for Disease Control. Her co-authors are from the National Microbiology Laboratory in Winnipeg, Quebec’s Public Health Institute, Public Health Ontario and a variety of universities across the country.

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