The difference in age structure and aging population level was an important factor that caused the difference in COVID-19’s case fatality rate (CFR) in various regions. To eliminate the age effect on estimating the CFR of COVID-19, our study applied nonlinear logistic model and maximum likelihood method to fit the age-fatality curves of COVID-19 in different countries and regions. We further computed the standardized mortality ratio from the age-fatality curves of COVID-19 in the above regions and found that the risk of COVID-19 death in Wuhan was of a moderate level, while the non-Hubei region was even lower, compared with other regions. Regarding the disparity of CFRs among different regions in the country, we believed that there might be an unascertained phenomenon in high-endemic regions. Based on age-fatality rate curves, we estimated unascertained rates in cities with severe epidemics such as Wuhan and New York, and it was found that the total unascertained rates in Wuhan and New York were 81.6% and 81.2%, respectively. Meanwhile, we also found that the unascertained rates varied greatly with age.

年龄结构和人口老龄化水平的差异是造成各地区COVID-19病死率（CFR）差异的重要因素。为了消除年龄对估计 COVID-19 CFR 的影响，我们的研究应用非线性逻辑模型和最大似然法来拟合不同国家和地区的 COVID-19 年龄-死亡率曲线。我们进一步根据上述地区的COVID-19年龄死亡率曲线计算标准化死亡率，发现武汉市的COVID-19死亡风险处于中等水平，而非湖北地区则更低。与其他地区。对于全国不同地区病死率的差异，我们认为高发地区可能存在未查明的现象。根据年龄死亡率曲线，我们估算了武汉、纽约等疫情严重城市的未确定率，发现武汉和纽约的总未确定率分别为81.6%和81.2%。同时，我们还发现，未确定的比率随年龄变化有很大差异。