COVID-19 vaccine effectiveness against death in Japan remains unknown. Furthermore, although evidence indicates that healthcare capacity influences case-fatality risk (CFR), it remains unknown whether this relationship is mediated by age. With a modeling study, we analyzed daily COVID-19 cases and deaths during January–August 2021 by using Tokyo surveillance data to jointly estimate COVID-19 vaccine effectiveness against death and age-specific CFR. We also examined daily healthcare operations to determine the association between healthcare burden and age-specific CFR. Among fully vaccinated patients, vaccine effectiveness against death was 88.6% among patients 60–69 years of age, 83.9% among patients 70–79 years of age, 83.5% among patients 80–89 years of age, and 77.7% among patients >90 years of age. A positive association of several indicators of healthcare burden with CFR among patients >70 years of age suggested an age-dependent effect of healthcare burden on CFR in Japan.

COVID-19 疫苗在日本的抗死亡效果仍然未知。此外，尽管有证据表明医疗保健能力会影响病死率 (CFR)，但尚不清楚这种关系是否受年龄影响。通过建模研究，我们分析了 2021 年 1 月至 8 月期间的每日 COVID-19 病例和死亡人数，方法是使用东京监测数据共同估计 COVID-19 疫苗针对死亡和特定年龄病死率的有效性。我们还检查了日常医疗保健操作以确定医疗保健负担与特定年龄 CFR 之间的关联。在完全接种疫苗的患者中，疫苗对死亡的有效性在 60-69 岁患者中为 88.6%，在 70-79 岁患者中为 83.9%，在 80-89 岁患者中为 83.5%，在>90岁。在70 岁以上的患者中，几个医疗负担指标与 CFR 呈正相关，这表明在日本医疗负担对 CFR 具有年龄依赖性影响。