Vaccination and Immunity toward Measles: A Serosurvey in Future Healthcare Workers

Measles is a very contagious infectious disease, and vaccination is the only medical aid to counter the spread of the infection. The aim of this study was to evaluate the influence of vaccination schedule and type of vaccine, number of doses, and sex on the immune response. In a population of Italian medical students (8497 individuals born after 1980 with certificate of vaccination and quantitative measurement of antibodies against measles), the prevalence of positive antibodies to measles and antibody titer was measured. Vaccination schedule such as number of doses and vaccine type (measles alone or combined as measles, mumps and rubella (MMR)) and sex were the variables considered to influence the immune response. The vaccination schedule depends on the year of birth: students born before 1990 were prevalently vaccinated once and with measles vaccine alone (not as MMR). One dose of vaccine induces a significantly (p < 0.0001) higher positive response and antibody titer than two doses, in particular when measles alone is used (p < 0.0001). Females have a significantly higher percentage of positive response (p = 0.0001) than males but only when the MMR formulation was used. Multiple linear regression confirms that sex significantly influences antibody titer when only MMR is used, after one (p = 0.0002) or two (p = 0.0060) doses. In conclusion, vaccination schedule and, partially, sex influence immune response to measles vaccination. Most notably, the measles vaccine alone (one dose) is more effective than one and two doses of MMR.