Study setting
Preschool
DISEASE
In order to achieve a good mixture of disease variability and severity in the study population (to maximise the external validity of the study results), the trial will be conducted in primary care practices and in the paediatric wards and outpatient departments of several general hospitals and university hospitals in the Netherlands. Preschool children aged 2 or 3 years will be recruited. The participating recruiting primary care practices are located in the southern and northern region of the Netherlands. The participating general hospitals are located throughout the country, as well as the participating university hospitals (Maastricht University Medical Centre, University Medical Centre Groningen, and Radboud University Medical Centre).The healthy children that contribute to the observational cohort study will be recruited at day-care centres, via centres for youth health care, and by means of primary care practices, and (social) media.