Persistence and Half-lives of Anti-measles and Anti-rubella Antibodies in Japanese Hospital Workers: A Longitudinal Study.

Abstract

Objective Antibody testing for endemic viruses in healthcare workers is used as an index of immunoprotection in Japan. However, it remains unclear how these antibody titers chronologically change and how they should be interpreted. Methods We retrospectively collected two sets of antibody titers to measles and rubella, measured in 2013 and within the preceding 5 years, in adult hospital workers by an enzyme-linked immunoassay and calculated in international units. Subjects infected with, or vaccinated against, these viruses over this period were eliminated. Seropositivities and geometric mean titers were analyzed. Decay rates and half-lives of antibodies were calculated using a mixed-effect model according to the subjects' ages and antibody titers. Results We analyzed 469 subjects for measles and 439 for rubella. Comparison with previous data revealed a mean measurement interval of 1,026 days between the previous and present tests, with seropositivity rates of 98.0% (previous) vs. 99.3% (present) for measles; 974 days and 90.7% vs. 94.9%, respectively, for rubella. For measles and rubella, 97.4% and 86.1%, respectively, of previously seropositive subjects remained positive in the present test. The geometric mean titers in the present and previous tests were 924.3 IU/mL and 853.2 IU/mL (measles) and 46.23 IU/mL and 40.78 IU/mL (rubella), respectively. In the mixed-effect model, measles and rubella antibody titers showed an increasing trend with age. Conclusion Seropositivities against measles and rubella can remain high for more than 5 years. Among adult hospital workers in Japan, the antibody titers against measles and rubella have a sufficient lifetime persistence.