Examination of Factors Associated with SARS-CoV-2 Serum Antibody Titers after mRNA Vaccination

Abstract

Serum SARS-CoV-2 S-IgG antibody of 383 hospital staff was measured approximately 6 months after the second vaccination (stage I-II) and approximately 5 months after the third vaccination (Stage III), to clarify factors associated with serum antibody titers acquired by mRNA vaccines against novel coronavirus (SARS-CoV-2). Several statistical analyses were performed on the relationships between background factors and serum antibody titers in 266 cases with no history of infection. In univariate analysis, factors affecting stage I-II antibody titers were age, blood type, underlying disease, pollen allergy, postvaccination side effects, exercise habits, snacking habits, and poor antibody production with other vaccines. Pollen allergy, postvaccination side effects, and poor antibody production with other vaccines were also associated with stage III antibody titers. In multivariate analysis, factors affecting stage I-II antibody titers were age, blood type, fever, snacking habits, and poor antibody production with other vaccines. In addition, factors affecting stage III antibody titers were gender, pollen allergy, and poor antibody production to other vaccines. Though the antibody titers of high-risk groups were lower than low-risk groups in the second vaccination, they became equivalent after the third vaccination. It means that third vaccination produced sufficient antibodies even in high-risk groups, and it contributes greatly to the prevention of aggravation.