1. These authors contributed equally to this article and share first authorship
2. Service of Epidemiology of Infectious Diseases, Department of Public Health and Surveillance, Scientific Institute of Public Health, Brussels, Belgium
3. National Reference Centre for measles, mumps and rubella, Service of Viral Diseases, Scientific Institute of Public Health, Brussels, Belgium
4. Infectious Disease Control and Vaccination, Flemish Agency for Care and Health, Brussels, Belgium
5. Infectious Disease Surveillance Unit, Agence pour une Vie de Qualité (AVIQ), Région Wallonne, Charleroi, Belgium
6. Health Inspection (Service de l'Inspection de l'Hygiène de la Commission communautaire commune), Brussels, Belgium