Vaccinated obese adults are twice as likely to develop influenza and influenza-like illnesses compared to vaccinated healthy weight adults, according to research published in the International Journal of Obesity.
Over 1,000 US adults who were either healthy weight, overweight or obese were vaccinated against flu during the 2013/14 and 2014/15 seasons.
Researchers from the University of North Carolina followed this with lab tests to establish whether they later developed flu or flu-like symptoms, and to assess to what degree their bodies went on to produce antibodies post-vaccination.
They found that a small number of patients did develop flu or flu-like illness even after they were vaccinated – with obese patients having double the relative risk of being affected.
Of the sample, 5.1% of patients with a healthy weight developed flu, compared to 9.8% of obese patients.
The results challenge the idea that blood tests alone can be used to determine whether a person has enough protection against influenza – and may even provide ‘misleading information’ for obese patients, the researchers warned.
Lead author Dr Scott Neidlich said: ‘Impaired cell functioning, despite the robust production of antibodies, may make vaccinated obese adults more susceptible to influenza infection. Alternative approaches may be needed to protect obese adults from both seasonal and pandemic influenza virus infections.’