Flu Season: Shot Not as Effective in Some Obese Patients

Researchers found another reason to maintain a healthy weight: flu prevention. The seasonal flu shot gives less immunity for overweight and obese people than for those in the healthy weight range.

University of North Carolina immunologist Patricia Sheridan and her colleagues published their findings this week in the International Journal of Obesity. The results came as no surprise to Sheridan, who for several years has observed that overweight mice exhibit a weakened immune response to the flu vaccine.

We wondered if this would be true in humans as well, she said.

Turns out, a study of 461 people showed her hunch was correct. Fifty percent of obese study participants had significant decreases in the amount of flu-fighting antibodies 12 months after getting the flu shot. Only 25 percent of those with healthy body mass indices had a significant decline in antibodies at the 1-year mark. The significant decline in antibodies in obese people may put them at a higher risk for getting sick from the influenza virus.

If Sheridan's findings hold true across the entire U.S. population, millions of people are at a greater risk for getting sick with influenza. The CDC reported that in 2010, 33.8 percent of adults and 17 percent of children and teens ages 2 to 19 were obese.

Sniffles, sneezes and chills - usually the common cold - are symptoms often confused with influenza, but getting the actual flu lands people in the hospital and about 36,000 people die from flu-related complications every year.

Though the flu shot may be less effective in some patients than others, Sheridan said people should still get it soon so it takes effect by the time this year's flu season is in full swing.

We still wholeheartedly believe that the flu vaccine is important and that obese people should be vaccinated, she said.