This study included 838 medical professionals who had provided consent. We asked them to report on previous histories of infection by measles, rubella, mumps, and varicella viruses as well as vaccination, and surveyed whether they carried an antibody to each of these viruses by determining the antibody titers. The determination was based on a PA method (a subject was considered as a candidate for vaccination if his/her titer was 1 : 128 or below) and EIA (less than 4.0) for measles, HI (1 : 8 or below) and EIA (less than 4.0) for rubella, and EIA (less than 4.0) for mumps and varicella. The subjects with a lower titer received vaccination if they so desired. The antibody titer to any of the viruses was low in 28% of the subjects; the percentage of the subjects being a candidate for vaccination was 7.4% for measles, 8.4% for rubella, 16.1% for mumps, and 0.8% for varicella. The self-reported prevalence rates and vaccination histories were poorly associated with the antibody titers. The antibody acquisition rates were 86.3 and 100.0% for PA and EIA, respectively, in measles, 93.3 and 98.3 for HI and EIA, respectively, in rubella, 82.9 in mumps, and 100.0 in varicella. Adverse events occurred due to vaccination at an incidence of 44.7% for measles/rubella virus, 37.1 for mumps, and 66.7 for varicella; all events were resolved, without serious symptoms possibly directly related to the vaccination. These results demonstrated that vaccination is also applicable to some individuals who report a history of a target disease or previous vaccination, suggesting the appropriateness of measuring antibody titers in all staff members. Furthermore, in this study, the effectiveness and safety of vaccination for those with a low titer were confirmed.
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