BMI, Age, and Gender Affect COVID-19 Vaccine Antibody Response

Miriam E. Tucker

March 03, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

The capacity to mount humoral immune responses to COVID-19 vaccinations may be reduced among people who are heavier, older, and male, new findings suggest.

The data pertain specifically to the mRNA vaccine, BNT162b2, developed by BioNTech and Pfizer. The study was conducted by Italian researchers and was published on February 26 as a preprint.

The study involved 248 healthcare workers who each received two doses of the vaccine. Of the participants, 99.5% developed a humoral immune response after the second dose. Those responses varied by body mass index (BMI), age, and gender.

"The findings imply that female, lean and young people have an increased capacity to mount humoral immune responses compared to male, overweight and older populations," said Raul Pellini, professor at the IRCCS Regina Elena National Cancer Institute, Rome, Italy, and colleagues.

"To our knowledge, this study is the first to analyze Covid-19 vaccine response in correlation to BMI," they note.

"Although further studies are needed, this data may have important implications to the development of vaccination strategies for COVID-19, particularly in obese people," they write.

If the data are confirmed by larger studies, "giving obese people an extra dose of the vaccine or a higher dose could be options to be evaluated in this population."

Results Contrast With Pfizer Trials of Vaccine

The BMI finding seemingly contrasts with final data from the phase 3 clinical trial of the vaccine, which were reported in a supplement to an article published December 31, 2020, in The New England Journal of Medicine. In that study, vaccine efficacy did not differ by obesity status.

Asked to comment, Akiko Iwasaki, PhD, professor of immunology at the Howard Hughes Medical Institute and an investigator at Yale University School of Medicine, New Haven, Connecticut, noted that although the current Italian study showed somewhat lower levels of antibodies in people with obesity compared to people who did not have obesity, the phase 3 trial found no difference in symptomatic infection rates.

"These results indicate that even with a slightly lower level of antibody-induced in obese people, that level was sufficient to protect against symptomatic infection," Iwasaki told Medscape Medical News.

Indeed, Pellini and colleagues point out that responses to vaccines against influenza, hepatitis B, and rabies are also reduced in those with obesity compared to lean individuals.

However, they say, it was especially important to study the effectiveness of COVID-19 vaccines in people with obesity, because obesity is a major risk factor for morbidity and mortality in COVID-19.

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BB Lee