Impact of Mass Screening on the Number of Confirmed Cases, Recovered Cases, and Deaths Due to COVID-19 in Iran: An Interrupted Time Series Analysis

Background: Mass screening for the coronavirus disease 2019 (COVID-19) began in Iran on March 23, 2020, with the purpose of improving early detection of patients for their own health and to prevent onward transmission to others. In this study, we evaluated the impact of the change towards mass screening on new cases reported, cases recovered, and deaths due to COVID-19. Methods: This study analyzed the daily reports on the number of new cases confirmed by polymerase chain reaction (PCR) testing, cases recovered, and deaths due to COVID-19 provided to the Ministry of Health and Medical Education of Iran. Changes in trends on these outcomes were evaluated using interrupted time series analysis. Results: From February 19 to May 6, 2020, a total of 519544 COVID-19 tests were done and 101650 diagnoses were made (case/ test ratio 19.6%). For the same period, 6418 deaths due to COVID-19 were reported (case fatality ratio 6.3%). The number of cases detected increased significantly over the period of scale-up of mass screening (P=0.003), as did the number of recovered cases (P=0.001). The number of deaths due to COVID-19 did not change before versus after mass screening. Conclusion: Following the scale-up of mass screening for COVID-19 in Iran, the rate of new cases detected and reported recovered accelerated significantly. Mass screening is likely to have detected many mild and asymptomatic cases that were infectious. Our data support the role that mass screening, coupled with isolation and contract tracing, can have in slowing the COVID-19 epidemic.