Abstract Background The clustering of metabolic abnormalities may weaken vaccine-induced immunity, but epidemiological data regarding SARS-CoV-2 vaccines are scarce. The present study aimed to examine the cross-sectional association between metabolic syndrome (MetS) and humoral immune response to Pfizer–BioNTech vaccine among the staff of a research center for medical care in Japan. Methods Participants were the staff (aged 21–75 years) of the National Center of Global Health and Medicine who had completed the second dose of...