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Influenza vaccine not as effective in adults who are obese

People who are obese were still twice as likely to develop influenza or influenza-like illnesses than others of healthy weight, despite receiving an influenza vaccine, according to research recently published in the International Journal of Obesity.

“Influenza infects 5% to 15% of the global population each year, and obesity has been shown to be an independent risk factor for increased influenza-related complications including hospitalization and death. However, the risk of developing influenza or [influenza-like illness] in a vaccinated obese adult population has not been addressed,” Scott D. Neidich, PhD, postdoctoral researcher, Human Vaccine Institute, Duke University, and colleagues wrote.

Researchers noted that obesity affects 37% of U.S. adults. Another recent study found that nearly one in three children and adults globally were affected by excess weight in 2015, and the percentage of people dying from health conditions stemming from being overweight or obese is rising.

Neidich and colleagues took serum samples from 1,022 adults who were healthy weight, overweight or obese before and after they had received the seasonal trivalent inactivated influenza vaccine during the 2013 to 2014 and 2014 to 2015 influenza seasons. Of the participants, 27% were healthy weight, 28% were overweight and 44% were obese. Symptom scores and laboratory tests ascertained if a vaccinated participant had influenza or influenza-like illness and to which degree their bodies produced influenza-fighting antibodies following vaccination.

Researchers found that among the obese participants, 9.8% had either confirmed influenza or influenza-like illnesses, compared with 5.1% of those of healthy weight. In addition, when compared with those at healthy weight who were vaccinated, obese participants had double the risk for influenza or influenza-like illness (RR = 2.01; 95% CI, 1.12-3.6). Also, seroprotection or seroconversion rates were not different between healthy weight and obese adults with influenza or influenza-like illnesses.

Neidich and colleagues also wrote that the present study confirmed earlier reports that hemaglutination inhibition antibody titers 30 days postvaccination in obese adults or children are either slightly higher or no different from vaccinated healthy weight individuals, but the present study found that a hemagglutination inhibition antibody titer of 40 or higher was not a serological correlate for vaccine-induced protection and did not prevent laboratory confirmed influenza and influenza-like illness in the participants who were obese. Additionally, microneutralization titers in the present study participants who were obese were also inadequate predictors of protection and these studies directly correlate with earlier studies in mice.

“Here, for the first time, we demonstrate that obese adult recipients of [seasonal trivalent inactivated influenza vaccine] have two times greater incidence of influenza and/or [influenza-like illness] despite being vaccinated,” Neidich and colleagues wrote. “Although our study does not compare vaccinated obese adults with unvaccinated obese adults, it is clear that vaccinated obese adults are at a higher risk for influenza and [influenza-like illness] compared to vaccinated healthy weight adults.” – by Janel Miller

Disclosure: The researchers report no relevant financial disclosures.