Early in 2021 the United Kingdom, along with several other countries, allowed mass gatherings as part of a series of controlled studies aimed at better understanding the role events could play in the pandemic. The goal was to inform policy - however early results have provided limited data on viral transmission.  As the Olympic games kick off in Tokyo, we delve into the research, asking what the limitations have been, if more data will become available and whether policy makers are likely to take the findings into account in the future. News: COVID and mass sport events: early studies yield limited insights News: Why England’s COVID ‘freedom day’ alarms researchers Podcast: Coronapod: does England's COVID strategy risk breeding deadly variants? Subscribe to Nature Briefing, an unmissable daily round-up of science news, opinion and analysis free in your inbox every weekday.   See acast.com/privacy for privacy and opt-out information.