Why do parents have their child vaccinated, or opt not to vaccinate? The SocioVax programme at RIVM explored that question through survey-based research. The results show that the vast majority of parents in the Netherlands consider it a social norm to have children vaccinated, even in groups in which vaccination uptake is lower than average. Care providers are an important source of information when making decisions about vaccination. This study helps us understand what different groups consider important in making decisions about vaccination, and what can help them in that process.