Will This Year's Flu Shot Be as Weak as Last Season's?

From Drugs.com - November 8, 2017

Will This Year's Flu Shot Be as Weak as Last Season's?

WEDNESDAY, Nov. 8, 2017 -- Lots of people came down with influenza last year despite getting a flu shot -- and researchers ca not promise this season's vaccine will be any more effective.

Last year's shot was only 20 percent to 30 percent effective because it was grown in eggs, according to the authors of a new report.

The egg process is not unusual. But a mutation in the predominant flu virus, called influenza A H3N2, limited the vaccine's potency, said study co-author Dr. John Treanor.

When H3N2 comes in contact with eggs, it changes, making it different from the virus that's circulating, he and his colleagues explained.

So last year, when H3N2 was the most common flu virus around, the shot was pretty lousy.

And what about the 2017-2018 flu season?

"It's too early to say which strain of flu will be predominant this year," said Dr. Daniel Jernigan, director of the influenza division at the U.S. Centers for Disease Control and Prevention.

"If it's an H1N1 year, then the vaccine is closer to 60 percent effective," Jernigan said.

Treanor pointed out that this year's flu vaccine contains the same strain of H3N2 as the 2016 vaccine, so if the new flu season is dominated by H3N2 again, it could be another bad season.

Treanor, a professor of infectious diseases at the University of Rochester in New York, said major efforts are under way to understand the factors that contribute to the less-than-perfect protection of flu vaccines.

"There are some emerging new findings that can contribute to developing better vaccines in the future," he said.

Growing influenza virus in eggs, then inactivating it and purifying it is the traditional method. "But there are some downsides to using chicken eggs as the production material," Treanor noted.

Two new methods of producing vaccines are being tried, he said.

One approach -- using animal cells as the production material -- allows the use of more standardized methods.

"Another approach is to use DNA techniques and to synthesize the vaccine directly from the genetic sequence of the virus," Treanor said.

Both these methods -- cell culture (Flucelvax) and DNA (Flublok) -- are licensed by the U.S. Food and Drug Administration.

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