Two cases of mild IgM-negative measles in previously vaccinated adults, the Netherlands, April and July 2011.

We describe two cases of mild, modified measles in fully vaccinated adults in the Netherlands. The mildness of disease, the lack of an IgM antibody response, the relatively low amounts of virus detected and the fact that no additional cases were reported, suggests that these vaccinated patients were less contagious than unvaccinated patients.