Untimely Reopening? Increase in the Number of New COVID‐19 Cases After Reopening in One Brazilian State
采用合成控制法评估巴西圣卡塔琳娜州2020年4月22日重新开放商业活动对每日新冠肺炎病例发病率的影响，发现重新开放导致病毒传播加快，后续感染中13.8%至50%可归因于此。
Abstract Santa Catarina was one of the first Brazilian states to allow businesses to reopen on 22 April 2020. I apply the synthetic control method to evaluate the impact of the reopening on incidence of daily COVID‐19 cases in Santa Catarina, including 17 Brazilian states in the donor pool. Conclusions about causality between the government measures and the infection spread can be made, although with caution, given the setup of a natural experiment and not actually randomly assigned treatment. The results are robust and show that the reopening leads to a faster spread of the virus, causing between 13.8% and 50% of all infections recorded in the following weeks. This study corroborates the recommendation for policies limiting circulation of people as a means to mitigate the spread of novel infectious diseases.