Flu shot only 19% effective this winter

Flu shot only 19% effective this winter
Flu vaccines were only 19% effective in preventing doctor visits for influenza this season, one of the lowest rates in the past decade, the Centers for Disease Control and Prevention said Thursday.
Health officials had predicted flu shots would be less protective than usual this year. That’s because the viruses used to make the flu shots weren’t a good match for the dominant strains of influenza in circulation, said Brendan Flannery, an epidemiologist in the CDC’s influenza division.
Scientists face a difficult challenge each year when selecting the virus strains to be included in seasonal flu shots, said Andrew Pekosz, an associate professor at the Johns Hopkins Bloomberg School of Public Health in Baltimore. That’s because flu viruses, unlike the measles or polio viruses, undergo significant genetic changes each year. So the vaccine needs to change every year, too.
Scientists from the CDC and Food and Drug Administration survey the dominant flu strains annually and make their selections in February, Flannery said. That gives manufacturers about six months to produce the vaccines, which ship out to clinics the following fall. Last year, however, flu viruses began mutating almost as soon as companies began production.
“This is a perfect example of what happens when the virus and the vaccine don’t synchronize,” Pekosz said.
In the past decade, effectiveness rates for flu shots have ranged from 10% to 60%, according to the CDC.

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