Two cases of mild IgM-negative measles in previously vaccinated adults, the Netherlands, April and July 2011 van den Hoek, A and Sonder, G J and Scholing, M and Gijselaar, DB and van Binnendijk, R S, Eurosurveillance, 16, 20028 (2011), https://doi.org/10.2807/ese.16.48.20028-en