Sex–associated differences between body mass index and SARS‐CoV‐2 antibody titers following the BNT162b2 vaccine

Objective We investigated the sex-associated difference in the impact of obesity on antibody response to COVID-19 vaccine. Methods This study included 2,435 healthcare workers who received two doses of the BNT162b2 vaccine and participated in a serological survey, wherein they were tested for anti-SARS-CoV-2 spike IgG antibodies and asked for information on height, weight, and vaccination history via a questionnaire. We used multivariable linear regression analysis to estimate the geometric mean titers (GMT) of antibodies for each sex and body mass index (BMI) category. Results The relationship between BMI and anti-SARS-CoV-2 spike IgG titers markedly differed by sex (P for interaction=0.04). Spike IgG antibody titiers tended to decrease with increasing BMI in men (P for trend=0.03); GMT [95% CIs] were 6,093 [4,874–7,618] and 4,655 [3,795–5,708] for BMI <18.5 and ≥30 kg/m2, respectively. In contrast, spike IgG antibody titiers did not significantly differ across BMI categories in women (P for trend=0.62); GMT [95% CIs] were 6,171 [5,714–6,665] and 5,506 [4,404–6,883] for BMI <18.5 and ≥30 kg/m2, respectively. Conclusions Higher BMI was associated with lower titers of SARS-CoV-2 spike antibody in men but not in women, suggesting the need for careful monitoring of vaccine efficacy in obese men, who are at high risk of severe COVID-19 outcome.