AbstractBackgroundBehavioural, environmental, social and systems interventions (BESSIs) remain important for controlling the COVID-19 pandemic in addition to vaccination. However, people’s adoption of BESSIs may decrease as vaccination rates increase due to reductions in the perceived threat of disease, and changes in risk perceptions of behaviours that increase the chance of infection. Thus, we examined predictors of and changes over time in reports of mask wearing and physical distancing and whether changes in mask wearing and physical distancing differed by vaccination status during the main 2021 COVID-19 vaccine roll-out period in Switzerland.MethodsWeekly online cross-sectional surveys (26 April 2021 to 1 August 2021) among people 18–79 years old in Switzerland,N= 6308 observations and 5511 cases. Logistic regression models using generalized estimating equations.ResultsReports of being vaccinated increased, while mask wearing and physical distancing decreased over time. This decrease was similar regardless of vaccination status. However, the level of reported mask wearing and physical distancing remained higher among vaccinated people. Older, female, and Italian language region respondents also had higher odds of reporting mask wearing and physical distancing.ConclusionsAdoption of COVID-19 preventive behaviours is associated with demographics and vaccination status. Further research is needed to understand the reasons why people who are not vaccinated are less likely to adopt preventive behaviours, including that they may have fewer social and environmental opportunities to do so.