Obesity Affects Influenza Vaccine Response

Larry Hand

October 25, 2011 — As the influenza season opens this month, researchers at the University of North Carolina at Chapel Hill warn for the first time that obese individuals may be getting less protection from vaccines than healthy-weight people. They reported their conclusions in an article published online October 25 in the International Journal of Obesity.

In an ongoing study involving patients getting vaccinated at an academic outpatient center, results from the first 2 years indicate that higher body mass index (BMI) is associated with a larger drop in influenza antibodies 12 months after vaccination with trivalent influenza vaccine. Previous research had linked obesity to risk for influenza infection, but this is the first time researchers have tested for antibodies a year after vaccination.

Using serum tests just after vaccination, Patricia Sheridan, PhD, from the Department of Nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, and colleagues found that weight did not make a significant difference in the initial response to trivalent influenza vaccine. However, in testing for CD8+ T-cell responses to vaccines 12 months later, the researchers discovered that as obesity levels increased, influenza antibodies decreased up to 4-fold. The CD8+ T-cells do not prevent infection by influenza, but they do help decrease severity and speed up viral clearance.

“These results suggest that overweight and obese people would be more likely than healthy weight people to experience flu illness following exposure to the flu virus,” Melinda Beck, PhD, professor and associate chair of nutrition at the University of North Carolina Gillings School of Global Public Health and senior author, said in a statement. “These new findings seem to give us a reason why obese people were more susceptible to influenza illness during the H1N1 pandemic compared to healthy weight people.”

 Researchers tested 461 adult patients aged 18 years or older during the 2009 influenza season, as well as 74 patients for the 2010 season. Of all the participants, 29.7% were healthy-weight individuals (BMI, 18.5 – 24.9 kg/m2), 33.4% were overweight (BMI, 25 – 29.9 kg/m2), and 35.5% were obese (BMI, ≥30 kg/m2). The remaining 1.4% were underweight.

Twelve months after vaccination, 50% of the obese patients showed at least a 4-fold decrease in antibody titers to 2 influenza strains. In comparison, less than 25% of the healthy-weight patients experienced similar large decreases in antibody titers.

Obesity also has been shown to reduce antibody response to hepatitis B vaccine in adults, and tetanus vaccine in children.

According to the World Health Organization, more than 10% of the world population is obese, and more than two thirds of the US population is overweight or obese.

Int J Obes. Published online October 25, 2011. Full text