Background: Following the recognition of a measles case in a hospital in The Netherlands, health care workers (HCW) from the premises were screened by a commercial enzyme immunoassay (EIA) for measles IgG to identify persons at risk for measles. At least 10% of the HCW were tested measles IgG-negative. As this was considered an unusually high proportion, we hypothesized suboptimal sensitivity of EIAs, especially in medical personnel that had vaccine-induced immunity rather than antibodies resulting from natural infection. Objectives: To determine (vaccine-induced) measles immunity in HCW, using different EIAs compared to the plaque reduction neutralization (PRN) test, the best surrogate marker for vaccine efficacy and immune protection. Study design: Sera from HCW were tested for measles IgG antibodies in three commercial EIAs, in a bead-based multiplex immunoassay (MIA) and in the PRN test, and evaluated against age and vaccination history of the HCW. Results: Of the 154 HCW, born between 1960 and 1995, 153 (99.4%) had protective levels of measles antibodies (PRN > 120 mI U/ml). The three EIAs failed to detect any measles IgG antibodies in approximately 10% of the HCW, while this percentage was approximately 3% for the MIA. Negative IgG results rose to 19% for individuals born between 1975 and 1985, pointing to an age group largely representing vaccinated persons from the first measles vaccination period in The Netherlands. Conclusion: The results show limitations in the usefulness of current EIA assays for determining protective measles antibodies in persons with a vaccination history.

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Journal of Clinical Virology
Department of Virology

Dorigo-Zetsma, J. W., Leverstein-Van Hall, M., Vreeswijk, J., de Vries, J., Vossen, A., ten Hulscher, H. I., … van Binnendijk, R. (2015). Immune status of health care workers to measles virus: Evaluation of protective titers in four measles IgG EIAs. Journal of Clinical Virology, 69, 214–218. doi:10.1016/j.jcv.2015.06.095