Increased Intensity Of PCR Testing Reduced COVID-19 Transmission Within Countries During The First Pandemic Wave.

Experts agree that reverse transcription-polymerase chain reaction (PCR) testing is critical in controlling coronavirus disease 2019 (COVID-19), but decision-makers disagree on how much testing is optimal. Controlling for interventions and ecological factors, we used linear regression to quantify testing's impact on COVID-19's average reproduction number, representing transmissibility, in 173 countries and territories, accounting for 99% of the world's COVID-19 cases, during March to June 2020. Amongst interventions, PCR testing had the greatest influence-a ten-fold increase in the ratio of tests to new cases reported reduced the average reproduction number by 9% across a range of testing levels. Our results imply that mobility reductions (e.g., shelter-in-place orders) were less effective in developing countries than in developed countries. Our results help explain how some nations achieved near-elimination of COVID-19 and the failure of lockdowns to slow COVID-19 in others. Our findings suggest that World Health Organization and other testing benchmarks are insufficient for COVID-19 control. Increased testing and isolation may represent the most effective, least costly alternative in terms of money, economic growth and human life for controlling COVID-19. [Editor's Note: This Fast Track Ahead Of Print article is the accepted version of the peer-reviewed manuscript. The final edited version will appear in an upcoming issue of Health Affairs.].