Obesity reduces influenza vaccine effectiveness

US researchers compared the responses of 500 obese, overweight and healthy weight people receiving the 2009–10 seasonal trivalent vaccine.

They noted higher antibody titres among individuals with high BMI one month after vaccination, but there was a more pronounced drop-off as time passed.

Among 74 participants tested 12 months later, 50% of high BMI study participants showed a fourfold decrease in titres compared to fewer than 25% of healthy weight study participants.

Infection-controlling CD8+ T cells were also “defective” in obese individuals, as they showed a much reduced response when blood samples were exposed to a flu virus strain 11 months post-vaccination.

Influenza-specific CD8+ T cells do not protect against infection, the authors said, but instead act to limit progression of disease and allow for more rapid viral clearance.

“We report here, for the first time, that influenza vaccine levels