1 November 2011
The first study to examine how obesity affects response to influenza vaccination has found antibody levels against flu virus drop off rapidly and a specific blood cell response is poorer.
US researchers compared the responses of 500 obese, overweight and healthy weight people receiving the 2009–2010 seasonal influenza vaccine.
They noted that individuals with a high body mass index (BMI) had higher antibody levels one month after vaccination, but these levels showed a more pronounced drop-off as time passed than levels in healthy weight individuals.
Among 74 people tested 12 months later, antibody levels had decreased fourfold in half of those with a high BMI compared with fewer than a quarter of those with a healthy weight.
Infection-controlling blood cells of a specific type were also "defective" in obese individuals, as their response was much poorer when blood samples were exposed to flu virus 11 months after vaccination.
These influenza-specific cells (CD8+ T cells) do not protect against infection, the authors said, but instead limit the disease progressing and allow the virus to be cleared from the body faster.
"We report here, for the first time, that influenza vaccine antibody levels decline significantly and CD8+ T cell responses are defective in obese compared with healthy weight individuals," the authors said.
It was first noticed during the 2009 swine flu pandemic that obese people were at heightened risk from the virus, but until now the mechanism has not been understood, the researchers said.
The vaccine received by the study participants included 3 influenza virus strains - one influenza B strain and two influenza A strains - but did not include the pandemic swine flu strain.
The researchers concluded that as global obesity levels increased, so too might deaths from influenza.
Last Reviewed: 04 November 2011