Flu Shot: Good but Not Perfect

Oct 25, 2011 6:30pm

A new review of the flu shot’s effectiveness has found considerable room for improvement. But the vaccine is still our best defense against the virus for now, experts say.

The trivalent flu shot, which is the one offered at most doctors’ offices and pharmacies, reduced the risk of illness 59 percent of the time, according to the review of 10 studies that spanned 12 flu seasons. The vaccine is designed to guard against the three most popular flu strains each season, which in 2012 include H1N1, H3N2 and influenza B.

“The ongoing public health burden caused by seasonal influenza and the potential global effect of a severe pandemic suggests an urgent need for a new generation of more highly effective and cross-protective vaccines that can be manufactured rapidly,” Michael Osterholm at  the University of Minnesota and colleagues reported today in Lancet Infectious Diseases. “In the meantime, we should maintain public support for present vaccines that are the best intervention available for seasonal influenza.”

The ever-evolving flu virus complicates the development of vaccines, which are strain-specific.

“That’s why we need a new vaccine every year,” said Dr. William Schaffner, chairman of preventive medicine at Vanderbilt University Medical Center. But scientists are working toward  a stronger, more universal vaccine that could be a one-shot deal — with the occasional booster.

Schaffner said the current vaccines are good but not great. But paraphrasing French philosopher Voltaire, he warned that waiting for perfect is the greatest enemy of the current good.

“While we hope and wait for a perfect vaccine, we’ve got a good one that’s capable of preventing influenza and its complication,” Schaffner said. “It can’t prevent every instance, but it can prevent many. And that’s a good thing.”

The 59 percent effectiveness of the vaccine suggested by the review challenges previous estimates, which range from 70 to 90 percent. In a commentary also published in Lancet Infectious Diseases, Heath Kelly at  the Victorian Infectious Diseases Reference Laboratory in Melbourne, Australia, and Marta Valenciano at EpiConcept in Paris, argue those estimates should be revisited.

“Now might also be an appropriate time to use revised estimates of the most probable effectiveness of influenza vaccines to re-examine the effectiveness and cost-effectiveness of some policy options,” they wrote.

The U.S. Centers for Disease Control and Prevention recommends that anyone older than 6  months get a flu shot every year. But less than half of eligible American’s got vaccinated last year.

“There’s still time to get vaccinated,” said Schaffner. “It’s widely available and absolutely everybody should go out and get it.”

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