Human behaviour – by private citizens, professionals and care workers – plays a key role in the prevention, timely detection and effective treatment of disease. The COVID-19 pandemic clearly demonstrates the importance of large-scale behavioural change. Testing, physical distancing and vaccinating were essential to an effective response. Access to current behavioural knowledge and practically applicable operational perspectives supported policy-makers, professionals and care workers in designing the desired behavioural changes. Examples include knowledge about building public support for current or future measures, or about effective communication. The possible societal impact of measures on e.g. mental health were also taken into account.