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Obesity may decrease effectiveness of the flu shot

Consumer Reports News: October 25, 2011 04:48 PM

That’s the finding from a prospective observational study published today in the International Journal of Obesity, comparing the protective antibody levels and T-cell responses to the seasonal flu vaccine in overweight, obese, and healthy weight adults.

At the start of the study, researchers at the University of North Carolina Family Medicine Center in Chapel Hill collected blood samples from 499 adults who received the 2009-2010 flu vaccine. At one month after vaccination and again after 12 months had passed, the researchers collected blood samples from the participants and measured protective antibody levels, which provide protection against infection, and the response of CD8+ T cells, white blood cells play a key role in limiting the spread and severity of infection.

Initially, all adults in the study had a similar robust response to the vaccine, but at 12 months, more than 50 percent of the adults who were obese experienced a four-fold plunge in antibody levels. Fewer than 25 percent of the healthy weight adults experienced the same decrease. And blood samples taken from obese people showed fewer functioning CD8+ T cells in response to the flu—just 25 percent, compared with 75 percent in healthy weight participants.

While more research is needed, this study’s findings add to a growing body of evidence indicating that obesity itself suppresses the immune system. During the 2009 H1N1 outbreak, for example, experts associated obesity with flu complications. This is cause for concern, given that recent estimates from the Centers for Disease Control and Prevention (CDC) show that 34 percent of American adults are considered obese.

Bottom line: Over the last 3 decades, the number of flu-associated deaths in the U.S. has ranged from a low of 3,000 to a high of 49,000, and the flu vaccine is the single most cost-effective way of preventing it. The CDC recommends the annual flu shot for all Americans older than 6 months, and continues to stress the importance of getting the vaccine for high-risk individuals, including pregnant women, young children, adults over 65, and anyone with an underlying chronic disorder, such as asthma, heart disease, or immune suppression.

And don’t rely on the flu shot alone—take these additional steps to reduce your flu risk: wash your hands, avoid close contact with sick people, get plenty of sleep, and quit smoking.

Find out why you need an annual flu shot and which supplements might help prevent the seasonal flu.

Obesity is associated with impaired immune response to influenza vaccination in humans [International Journal of Obesity]
Study: Obesity limits effectiveness of flu vaccines [UNC Healthcare]
Questions & Answers: Seasonal Flu Vaccine [CDC]
Adult Obesity Prevalence in Canada and the United States [CDC]

Ginger Skinner

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