Massachusetts General Hospital, Boston, Massachusetts, United States of America.
Harvard Medical School, Boston, Massachusetts, United States of America.
PLoS Med. 2020 Aug 11;17(8):e1003244. doi: 10.1371/journal.pmed.1003244. eCollection 2020 Aug.
Social distancing measures to address the US coronavirus disease 2019 (COVID-19) epidemic may have notable health and social impacts.
We conducted a longitudinal pretest-posttest comparison group study to estimate the change in COVID-19 case growth before versus after implementation of statewide social distancing measures in the US. The primary exposure was time before (14 days prior to, and through 3 days after) versus after (beginning 4 days after, to up to 21 days after) implementation of the first statewide social distancing measures. Statewide restrictions on internal movement were examined as a secondary exposure. The primary outcome was the COVID-19 case growth rate. The secondary outcome was the COVID-19-attributed mortality growth rate. All states initiated social distancing measures between March 10 and March 25, 2020. The mean daily COVID-19 case growth rate decreased beginning 4 days after implementation of the first statewide social distancing measures, by 0.9% per day (95% CI -1.4% to -0.4%; P < 0.001). We did not observe a statistically significant difference in the mean daily case growth rate before versus after implementation of statewide restrictions on internal movement (0.1% per day; 95% CI -0.04% to 0.3%; P = 0.14), but there is substantial difficulty in disentangling the unique associations with statewide restrictions on internal movement from the unique associations with the first social distancing measures. Beginning 7 days after social distancing, the COVID-19-attributed mortality growth rate decreased by 2.0% per day (95% CI -3.0% to -0.9%; P < 0.001). Our analysis is susceptible to potential bias resulting from the aggregate nature of the ecological data, potential confounding by contemporaneous changes (e.g., increases in testing), and potential underestimation of social distancing due to spillover effects from neighboring states.
Statewide social distancing measures were associated with a decrease in the COVID-19 case growth rate that was statistically significant. Statewide social distancing measures were also associated with a decrease in the COVID-19-attributed mortality growth rate beginning 7 days after implementation, although this decrease was no longer statistically significant by 10 days.
为应对美国 2019 年冠状病毒病（COVID-19）疫情而采取的社会隔离措施可能会对健康和社会产生显著影响。
我们进行了一项纵向的预-后测比较群组研究，以估计在全美实施全州范围的社会隔离措施之前和之后 COVID-19 病例增长的变化。主要暴露因素是实施全州范围的社会隔离措施之前（14 天之前至实施后的 3 天）与之后（开始实施后的第 4 天至最长 21 天）的时间。我们还研究了作为次要暴露因素的全州范围内对内部流动的限制。主要结局是 COVID-19 病例增长率。次要结局是 COVID-19 归因死亡率增长率。所有州都在 2020 年 3 月 10 日至 3 月 25 日之间开始实施社会隔离措施。在实施全州范围的社会隔离措施的第 4 天开始，每日 COVID-19 病例增长率平均每天下降 0.9%（95%CI -1.4%至-0.4%；P < 0.001）。我们没有观察到在实施全州范围内对内部流动的限制之前与之后每日病例增长率的统计学显著差异（每天 0.1%；95%CI -0.04%至 0.3%；P = 0.14），但全州范围内对内部流动的限制与全州范围的社会隔离措施的独特关联之间存在很大困难。在社会隔离措施开始后的第 7 天，COVID-19 归因死亡率增长率平均每天下降 2.0%（95%CI -3.0%至-0.9%；P < 0.001）。我们的分析容易受到生态数据总体性质、同期变化（例如，检测量增加）的潜在混杂以及由于邻近州的溢出效应而导致对社会隔离措施的潜在低估的潜在偏差的影响。
全州范围的社会隔离措施与 COVID-19 病例增长率的下降相关，且具有统计学意义。在实施全州范围的社会隔离措施后的第 7 天，COVID-19 归因死亡率增长率也开始下降，尽管在第 10 天不再具有统计学意义。
