10-Year survey on serum antibody positivity rates and titers for measles and rubella in healthcare workers; an observational study at a Japanese university hospital.

BACKGROUND

We evaluated the effect of the two-dose vaccination strategy, which has been a widely adopted as childhood routine schedule worldwide to acquire herd immunity, on healthcare workers (HCWs) in Japan.

METHODS

Between 2010 and 2019, antibody titers for measles and rubella were measured annually among newly employed HCWs at Osaka University Hospital, Japan, using Enzygnost® assays (Siemens Healthcare Diagnostics Co. Ltd., Marburg, Germany). The data were categorized by age to compare the antibody positivity rates and antibody titers among no-vaccine, single-dose, and two-dose groups.

RESULTS

Over the 10-year period, the annual antibody positivity rates for measles and rubella were 84.0%-95.3% and 90.0%-94.5%, respectively, without any particular trend. The antibody titers for measles (median [interquartile range]: 8.4 [3.9, 20] vs. 6.1 [3.5, 12]) and rubella (11 [5.5, 20] vs. 6 [3.7, 11]) were statistically lower (p < 0.001) in the two-dose generation than in the single-dose generation.

DISCUSSION: A shift from single-dose to two-dose vaccination did not yield an increase in antibody positivity rates for both measles and rubella among HCWs. Notably, antibody titers were significantly lower in the two-dose generation.

CONCLUSION

Despite several limitations, our data suggests a paradoxical vulnerability in young HCWs who received the two-dose vaccination in a view of sero-positivity rates.