Nightly News   |  October 25, 2011

Flu shots less effective in obese, study shows

People who are obese get less protection from an annual flu shot, a new study reveals. What makes flu shots less effective than many people believe? NBC News’ Robert Bazell has more.

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This content comes from a Full-Text Transcript of the program.

BRIAN WILLIAMS, anchor: As we mentioned, there's also this news tonight about the shot we're all told to get this time of year for the flu. New research suggesting it may not be as effective in warding off the flu as a lot of people have been led to think, especially for the people most at risk. Our report from our chief science correspondent, Robert Bazell .

ROBERT BAZELL reporting: The government has been recommending flu shots for 50 years.

Unidentified Medical Professional: You've had the flu shot before?

BAZELL: But today's study reveals they are often far less effective than many people believe.

Mr. MICHAEL OSTERHOLM (University of Minnesota): We don't have the data we need to support the kind of influenza programs in the elderly that we currently have.

BAZELL: Mike Osterholm and his team at the University of Minnesota found that because the vaccine often differs from the virus in circulation, the effectiveness varies from year to year, ranging from 16 percent to 76 percent, with an average of 59 percent, and that is in relatively young, healthy adults. But in most flu seasons, 90 percent of the hospitalizations and deaths are in the elderly, and it's in that group where the evidence for the vaccine 's effectiveness is the weakest. There are no randomized trials of the vaccine in people 65 or older, and the best observation is that the flu vaccine reduces hospitalizations in that group by 8.5 percent and deaths by 4.6 percent. The Centers for Disease Control , which sets national vaccine policy, does not disagree with the latest findings but points out the vaccine is the only one we've got, that it is safe and does save lives.

Dr. ANNE SCHUCHAT (Centers for Disease Control): I hope that people won't be scared about the vaccine or worried about the effectiveness.

BAZELL: Osterholm agrees that people should get the vaccine but says research for a more effective one should be a higher priority.

Mr. OSTERHOLM: We need new and better vaccines and fast.

BAZELL: And so for these people getting shots at a clinic set up by Maimonides hospital today, and others like them...

Medical Professional: There you go.

Unidentified Woman: Thank you so much .

Medical Professional: You're welcome.

BAZELL: ...the bottom line is get your vaccine , but know there's no guarantee it will always work. Robert Bazell , NBC News, New York.