Milder flu season may be due to a better flu vaccine match, report says

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By Shamard Charles, M.D.

This season’s flu vaccine is a good match for the virus strains in circulation, according to new data from the Centers for Disease Control and Prevention, explaining in part the lower severity of the season.

In its weekly report on Thursday, the federal agency said the interim estimate of the flu vaccine’s effectiveness against the H1N1 influenza strain, which has been dominant in the United States this year, was 47 percent. For context, at this time last year the midseason effectiveness of the vaccine was just 36 percent. The interim estimate covers October through February.

This season, nearly 90 percent of the flu cases tested by the CDC are turning out to be H1N1, the milder variety. Ten percent of people are still getting the H3N2 version of the flu, the stronger version that dominated last season.