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How the flu vaccine turned out to be a poor match for this year's flu

How the flu vaccine turned out to be a poor match for this year s flu LA Times


When it comes to developing a seasonal flu vaccine, researchers must take aim at an invisible target.

Not only are flu viruses constantly changing, drug manufacturers need to start producing their vaccines four to six months before the flu season starts. That means scientists must predict which virus will be most active months before it even appears.

Like weather forecasters, sometimes they get it right and sometimes they get it wrong. This season, it looks like they got it wrong.

On Thursday, the director of the Centers for Disease Control and Prevention warned that the flu shots and nasal sprays distributed this year may not be a good match for the most active virus now circulating in the U.S.


"Our recommendations were made back in February because we need time to produce a vaccine, and that's the problem," said Dr. Arnold Monto, an expert on infectious diseases at the University of Michigan School of Public Health. "It's the production lag."


n a good year, a seasonal flu vaccine can reach 70% efficacy. In a bad year, it can be much lower.

The vaccine for last year's flu season had an overall efficacy between 50% and 55%, said Dr. Joseph Bresee of the CDC's National Center for Immunization and Respiratory Diseases.

"In general our current influenza vaccine is a good vaccine, but it's not a great vaccine," Monto said. "We all recognize that we need improvement."

Still, Frieden said Americans should get vaccinated if they haven't already. "Though far from perfect, it still offers us the best chance for prevention," he said.

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Overall efficacy of 50% to 55% is not good.

But thanks for the explanation of why the vaccine is less helpful this year.

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