Impact of vaccination on measles, mumps, and rubella antibody titers in Japanese healthcare workers: An observational study

Given the complicated history of Japan's National Immunization Program, a significant proportion of Japanese people including healthcare workers (HCWs) still lack adequate immunity against measles, mumps, and rubella (MMR), resulting in occasional outbreaks. In 2014, the Japanese Society of Infection Prevention and Control (JSIPC) published vaccination guidelines for HCWs. We evaluated antibody titers before and after MMR vaccination in HCWs at the Nara Medical University Hospital, the attainment rate of the target antibody titers defined by the JSIPC guidelines, and the safety of vaccines. We measured MMR antibody titers in HCWs, followed by inoculation with the respective monovalent vaccines and/or trivalent MMR (tMMR) vaccine according to the JSIPC guidelines. Among 467 HCWs evaluated, antibody titers against measles and mumps measured using the IgG-enzyme immunoassay increased from 11.0 [interquartile range (IQR): 8.0-13.6] to 13.7 (IQR: 11.3-16.9; P < 0.001) and from 2.8 (IQR: 2.1-3.5) to 4.8 (IQR: 3.7-5.7; P < 0.001), respectively. By evaluating a logarithmic value of log(2)(X + 1) converted from an antibody titer X, antibody titers against rubella measured using the hemagglutination assay increased from 3.2 (IQR: 0-4.1) to 6.0 (IQR: 4.6-8.0; P < 0.001). Antibody titer elevated following tMMR vaccination was lower than that following monovalent vaccination in a single dose of the measles-containing, a single dose of the mumps-containing, and two doses of rubella-containing vaccine groups (P = 0.01, 0.01, and <0.001, respectively). After vaccination, 20.0%, 61.5%, and 46.2% of HCWs attained target antibody titers specified by the JSIPC guidelines for measles, rubella, and mumps, respectively. The systemic response in female HCWs who underwent monovalent mumps vaccination was statistically higher than that in others. Although the vaccination program for HCWs according to the JSIPC guidelines caused increased MMR antibody titers, the rates of attaining the target criteria were low.