Prior to the 2009 H1N1 influenza pandemic, obesity was not considered an underlying health condition that might place people at greater risk of serious seasonal flu-related complications. However, recent findings, such as this analysis of more than 80,000 H1N1 cases, suggest that obesity may impair the human body’s ability to fight the flu virus.
Now new research from the University of North Carolina at Chapel Hill shows that obesity may make annual flu shots less effective and that obese and overweight patients have a greater risk for more severe illness if they do come down with the flu.
In the study, researchers evaluated patients at a university clinic who were vaccinated in late 2009 with an inactivated trivalent influenza vaccine, the common flu vaccine for that time period. Within the first month after vaccination, all the individuals developed antibodies to flu viruses. But over time the antibody levels in the blood declined more rapidly in obese and overweight participants. Health Day reports:
Specifically, there was a fourfold decrease in antibody levels 11 months after vaccination in half of the obese patients, compared to one month post-vaccination. By contrast, less than 25 percent of healthy weight participants showed this degree of decrease in their antibody levels after 11 months, the researchers found.
In addition, a type of white blood cell called CD8+ T-cells, which play a key role in priming the body's immune system, doesn't work properly in heavier people. When vaccination doesn't stave off the flu, people must rely, in part, on these white blood cells to limit the spread and severity of the infection.
Study authors say that more research is needed to determine if obese or overweight individuals are more susceptible to the flu and if these patients would benefit from the double flu shot approach, during which people in high-risk populations are given one shot in early fall and another in January.
Previously: European experts debunk six myths about flu shot, FDA announces this year’s approved flu vaccines, Flu shot, please! and Study shows U.S. obesity rates will expand over next 40 years
Photo by Cindy Funk