1. National Coordination Centre for Communicable Disease Control The National Institute for Public Health and the Environment Bilthoven The Netherlands
2. Athena Institute, Faculty of Science VU University Amsterdam Amsterdam 1081 HV The Netherlands
3. NIVEL, The Netherlands Institute for Health Services Research Utrecht 3513 CR The Netherlands
4. Health, Medicine and Life Sciences Maastricht University Maastricht The Netherlands
5. Department of Primary and Community Care Radboud University Medical Centre Nijmegen The Netherlands