MEASLES IMMUNITY IN A POPULATION OF HEALTH-CARE WORKERS

OBJECTIVES: To evaluate measles seroprevalence among cohorts of new em ployees and to evaluate vaccine responses of susceptible adult healthc are workers. DESIGN: New employees were screened for measles susceptib ility as part of employee evaluations. Anti-IgG measles antibody tests were completed on 2,473 workers. Demographic, measles history, and me asles vaccination information was collected using a short questionnair e. Susceptible workers were vaccinated and screened for vaccine respon ses following vaccination. RESULTS: Ninety-three workers (4(%) were se ronegative, and 56 (2%) were equivocal. Individuals in the youngest co hort (born after 1956) were significantly more likely to be susceptibl e than those in the middle cohort (born 1951 to 1956) and those in the oldest cohort (born before 1951) (P<0.01). The middle cohort included eight (5%) of the 149 seronegative or equivocal workers. Among the me mbers of the youngest cohort, those from the United States were more l ikely to be susceptible (P<0.01) than those from outside the United St ates. Of the 106 vaccinated susceptible workers whose follow-up serolo gies were determined, 90 (85%) developed positive IgG serologies, six had equivocal results, and 10 were seronegative. Eleven of the 16 non- or hyporesponders were revaccinated and re-evaluated; nine developed low positive IgG antimeasles levels, one exhibited an equivocal respon se, and one failed to respond. CONCLUSIONS: A small but important prop ortion of healthcare workers are susceptible to measles. Whenever feas ible, measles immunity programs for healthcare workers should include workers born before 1957. Of workers born after 1956, those from outsi de the United States are more likely to be immune than workers from in side the United States. Using the currently available vaccine, revacci nation of initial non- or hyporesponders appears to be effective.