Since the COVID-19 pandemic first reached the United States, the case fatality rate has fallen precipitously. Several possible explanations have been floated, including greater detection of mild cases due to expanded testing, shifts in age distribution among the infected, lags between confirmed cases and reported deaths, improvements in treatment, mutations in the virus, and decreased viral load as a result of mask-wearing. Using both Florida line-level data and recently released (but incomplete) national line level data from April 1, 2020 to November 1, 2020 on cases, hospitalizations, and deaths--each stratified by age--we unpack the drop in case fatality rate (CFR). Under the hypothesis that improvements in treatment efficacy should correspond to decreases in hospitalization fatality rate (HFR), we find that improvements in the national data do not always match the story told by Florida data. In the national data, treatment improvements between the first wave and the second wave appear substantial, but modest when compared to the drop in aggregate CFR. By contrast, possibly due to constrained resources in a much larger second peak, Florida data suggests comparatively little difference between the first and second wave, with HFR slightly increasing in every age group. However, by November 1st, both Florida and national data suggest significant decreases in age-stratified HFR since April 1st. By accounting for several confounding factors, our analysis shows how age-stratified HFR can provide a more realistic picture of treatment improvements than CFR. One key limitation of our analysis is that the national line-level data remains incomplete and plagued by artifacts. Our analysis highlights the crucial role that this data can play but also the pressing need for public, complete, and high-quality age-stratified line-level data for both cases, hospitalizations, and deaths for all states.
翻译:自COVID-19大流行首次到达美国以来,病例死亡率急剧下降。一些可能的解释已经浮现出来,包括由于测试范围扩大,感染者年龄分布的变化,经证实的病例与报告死亡之间的时间差,治疗的改善,病毒突变,以及因戴面罩而减少的病毒负荷。利用佛罗里达州线级数据和最近公布的(但不完整)全国线级数据,从2020年4月1日至2020年11月1日,病例、住院治疗和死亡人数由年龄分解的死亡率下降率(CFR)上升。根据治疗效率的改善应当与住院死亡率下降相对应的假设(HFR ),我们发现国家数据的改善并不总是与佛罗里达州数据所讲述的情况一致。在国家数据中,第一波和第二波之间的治疗改善幅度似乎相当大,但与CFRFR总体下降相比,由于资源大幅下降,也许由于我们第二线的下降,佛罗里达州的数据显示第一波和第二波之间的差别相对较小,而且自4月1日以来,HFRFR的最新数据也显示,这种下降。