Date Time Mass testing with a short period of contact restrictions dramatically reduced SARS-CoV-2 infections In October 2020, Slovakia tested its whole population for SARS-CoV-2 infections, conducting more than five million rapid antigen tests. A pilot trial took place between 23 and 25 October in the country’s four most affected counties, followed by a round of national mass testing on 31 October and 1 November. High prevalence counties were again targeted with a subsequent round on 7 and 8 November. The analysis, which has not yet been peer-reviewed, was conducted in collaboration with the Slovak Ministry of Health. Using data on the proportions of those attending the mass testing that tested positive, the team estimated the combined impact of this mass testing with contact restrictions on SARS-CoV-2 infection prevalence.