Effects of a closed-loop system against SARS-CoV-2 at the Beijing 2022 Olympic Winter Games:a descriptive and modeling study

BACKGROUND:To assess the efficacy of the epidemic prevention measures of the“closed-loop”system adopted by the Beijing 2022 Olympic Winter Games(BOWG).METHODS:We retrospectively collected and analyzed information,including age,sex,nationality,vaccination status,date of diagnosis,and date of entry,from 280 SARS-CoV-2-positive individuals identified during the BOWG.A susceptibility-exposed-infectious-remove model was employed to evaluate the effectiveness of epidemic prevention strategies on controlling the spread of SARS-CoV-2 under different scenarios during the BOWG.RESULTS:Regarding SARS-CoV-2-positive cases,97.9%were imported,and 96.4%were asymptomatic.The median age was 37 years(range:29–47 years),and 73.9%were male,with the majority of cases being broadcasters and European attendees.Regarding vaccination status,93.5%were fully vaccinated,and six cases were considered to have been infected in the closed-loop system during the BOWG.Assuming that the BOWG adopted a semi-closed-loop management system,the cumulative number of confirmed cases would be 1,137 for quick quarantine measures(3 d later)implemented and 5,530 for delayed quarantine measures(9 d later)implemented.This modeling revealed that stringent pandemic prevention measures and closed-loop management effectively controlled the spread of SARS-CoV-2 during the BOWG.CONCLUSION:Imported cases are considered the main risk factor for SARS-CoV-2 transmission during mass gatherings,but a comprehensive closed-loop system could minimize transmission among attendees and general personnel.