Increased emergency room visits or hospital admissions in females after 12-month MMR vaccination, but no difference after vaccinations given at a younger age.

Highlights: [•] Child's sex was not associated with events following vaccines administered at 2, 4 and 6 months of age. [•] Females had a higher relative incidence of events following the 12-month vaccination, which contains MMR. [•] There were 192 excess events per 100,000 females vaccinated compared to the number of events that would have occurred in 100,000 vaccinated males. [•] Events we examined were emergency room visits and hospital admissions. [ABSTRACT FROM AUTHOR]