Background We assessed the added benefit and waning effectiveness of a third COVID-19 vaccine dose (original formula) for preventing COVID-19-related outcomes. Methods We used Medicare claims data to conduct a retrospective cohort study in U.S. community-dwelling Medicare Fee-for-Service beneficiaries aged ≥65 years during the BA.1/BA.2 Omicron period (December 19, 2021 – March 26, 2022). We estimated relative vaccine effectiveness (RVE) of 3 versus 2 doses of mRNA COVID-19 vaccines using marginal structural Cox regression models. Results Among 8,135,020 eligible beneficiaries, 73.3% were 3-dose vaccinated by March 26, 2022. At 14-60 days since vaccination, a third dose provided significant added benefit against COVID-19-related hospitalization for Moderna (RVE: 77.2%; 95% confidence interval (CI): 76.0%, 78.4%) and Pfizer-BioNTech (RVE: 72.5%; 95% CI: 70.8%, 74.0%). Added benefit was lower >120 days. For those with prior medically attended COVID-19 diagnoses, Pfizer-BioNTech provided an added benefit for 120 days, while Moderna provided some added benefit >120 days. Added benefit for either vaccine was higher against death compared to less severe outcomes, which still decreased >120 days. Conclusions A third dose COVID-19 vaccine provided significant added benefit against COVID-19-related hospitalization and death, even for beneficiaries with prior medically attended COVID-19 diagnoses. This added benefit decreased after 4 months.

中文翻译：

---

在 BA.1/BA.2 Omicron 期间，65 岁及以上的 Medicare 受益人第三剂 mRNA COVID-19 疫苗的相对有效性和减弱


背景 我们评估了第三剂 COVID-19 疫苗（原始配方）对预防 COVID-19 相关结局的额外益处和逐渐减弱的有效性。方法 我们使用 Medicare 索赔数据对 BA.1/BA.2 Omicron 期间（2021 年 12 月 19 日至 2022 年 3 月 26 日）年龄为 ≥65 岁的美国社区居住的 Medicare 按服务收费受益人进行回顾性队列研究。我们使用边缘结构 Cox 回归模型估计了 3 剂与 2 剂 mRNA COVID-19 疫苗的相对疫苗有效性 （RVE）。结果在 8,135,020 名符合条件的受益人中，截至 2022 年 3 月 26 日，73.3% 的人接种了 3 剂疫苗。在接种疫苗后 14-60 天，第三剂为 Moderna（RVE：77.2%;95% 置信区间 （CI）：76.0%，78.4%）和辉瑞-BioNTech（RVE：72.5%;95% CI：70.8%，74.0%）的 COVID-19 相关住院提供了显着的额外益处。额外的好处是较低的 >120 天。对于那些之前接受过 COVID-19 医学诊断的人，辉瑞-BioNTech 提供了 120 天的额外好处，而 Moderna 提供了一些额外的好处 >120 天。与较轻的结局相比，这两种疫苗的额外益处都更高，死亡结局仍缩短了 >120 天。结论 第三剂 COVID-19 疫苗对 COVID-19 相关住院和死亡提供了显着的额外益处，即使对于先前接受过 COVID-19 医疗诊断的受益人也是如此。这种额外的好处在 4 个月后减少。