Influenza vaccine less effective in overweight, obese people

Sheridan PA. Int J Obes. 2011;doi:10.1038/ijo.2011.208.

Obesity may render the annual influenza vaccine ineffective, according to data from researchers at the University of North Carolina at Chapel Hill. Their results suggest that BMI is associated with a decline in influenza antibody titers 12 months after vaccination.

"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 UNC Gillings School of Global Public Health, said in a press release.

According to Beck, previous studies have shown that obesity may impair the body's ability to fight influenza viruses. Their results may explain why those who are obese were more susceptible to influenza during the H1N1 pandemic vs. those who are healthy weight.

The researchers used a convenience sample to determine the antibody response to the 2009-2010 inactivated trivalent influenza vaccine in healthy weight, overweight and obese people 1 and 12 months after vaccination. Influenza-stimulated peripheral blood mononuclear cell cultures were used to measure CD8+ T-cell activation and interferon-gamma and granzyme B expression.

During the first year of the study, September 2009 to November 2009, researchers enrolled 499 participants who returned 28 to 35 days after vaccination for blood draw. At the beginning of the second year of the study, 74 participants involved in the first year of the study re-enrolled. Immune parameters in these patients were assessed 12 months after the 2009-2010 influenza vaccination.

At 11 months, about 50% of obese participants had a fourfold decrease in antibody titers compared with the first month after vaccination. Among healthy weight participants, however, fewer than 25% had a fourfold decrease in antibody titers. Additionally, about 75% of healthy weight participants had stable CD8+ T-cell activation and interferon-gamma and granzyme B expression vs. about 25% of obese participants.

"The findings also suggest overweight and obese people are more likely to become sicker and have more complications," Heather Paich, a doctoral student in Beck's lab, said in a press release. "That's because influenza-specific CD8+ T cells do not protect against infection, but instead act to limit the disease's progression and severity of disease."

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