Departamento de Epidemiologia, Instituto Nacional de Saúde Doutor Ricardo Jorge, Lisbon, Portugal.
Escola Nacional de Saúde Pública (ENSP/NOVA), Centro de Investigação em Saúde Pública (CISP/NOVA), Universidade NOVA de Lisboa, Lisbon, Portugal.
PLoS One. 2022 Sep 13;17(9):e0274008. doi: 10.1371/journal.pone.0274008. eCollection 2022.
Using data from electronic health registries, this study intended to estimate the COVID-19 vaccine effectiveness (VE) in the population aged 65 years and more, against symptomatic infection, COVID-19-related hospitalizations, and deaths, overall and by time since complete vaccination for the period February to September 2021.
We established a cohort of individuals aged 65 and more years old, resident in Portugal mainland, using the National Health Service User number to link eight electronic health registries. Outcomes included were symptomatic SARS-CoV-2 infections, COVID-19-related hospitalizations or deaths. The exposures of interest were the mRNA vaccines (Comirnaty or Spikevax) and the viral vector (Vaxzevria) vaccine. Complete schedule VE was estimated as one minus the confounder adjusted hazard ratio, for each outcome, estimated by time-dependent Cox regression with time-dependent vaccine exposure.
For the cohort of individuals aged 65-79 years, complete scheme VE against symptomatic infection varied 43 (95%CI: 37-49) (Vaxzevria) and 65 (95%CI: 62-68) (mRNA vaccines). This estimate was slightly lower in the ≥80 years cohort (53, 95%CI: 45-60) for mRNA vaccines). VE against COVID-19 hospitalization varied between 89% (95%CI: 52-94) for Vaxzevria and 95% (95%CI: 93-97) for mRNA vaccines for the cohort aged 65-79 years and was 76% (95%CI: 67-83) for mRNA vaccines in the ≥80 years cohort. High VE against COVID-19-related deaths was estimated, for both vaccine types, 95% and 81 (95%CI:76-86) for the 65-79 years and the ≥80 years cohort, respectively. We observed a significant waning of VE against symptomatic infection, with VE estimates reaching approximately 34% for both vaccine types and cohorts. Significant waning was observed for the COVID-19 hospitalizations in the ≥80 years cohort (decay from 83% (95%CI:68 to 91) 14-41 days to 63% (95%CI:37 to 78) 124 days after mRNA second dose). No significant waning effect was observed for COVID-19-related deaths in the period of follow-up of either cohort.
In a population with a high risk of SARS-CoV-2 complications, we observed higher overall VE estimates against more severe outcomes for both age cohorts when compared to symptomatic infections. Considering the analysis of VE according to time since complete vaccination, the results showed a waning effect for both age cohorts in symptomatic infection and COVID-19 hospitalization for the 80 and more years cohort.
本研究利用电子健康登记数据，旨在估计 65 岁及以上人群中 COVID-19 疫苗对症状感染、COVID-19 相关住院和死亡的有效性（VE），整体来看，以及自 2021 年 2 月至 9 月完全接种疫苗以来的时间。
我们建立了一个年龄在 65 岁及以上的人群队列，使用国家卫生服务用户编号将 8 个电子健康登记系统联系起来。研究结果包括有症状的 SARS-CoV-2 感染、COVID-19 相关住院或死亡。感兴趣的暴露因素是 mRNA 疫苗（Comirnaty 或 Spikevax）和病毒载体（Vaxzevria）疫苗。对于每个结果，通过时间依赖性 Cox 回归估计时间依赖性疫苗暴露的完整方案 VE，估计为每个结局的混杂因素调整后的危险比的倒数。
对于 65-79 岁年龄组，针对症状感染的完整方案 VE 分别为 43（95%CI：37-49）（Vaxzevria）和 65（95%CI：62-68）（mRNA 疫苗）。对于≥80 岁年龄组，mRNA 疫苗的这一估计值略低（53，95%CI：45-60）。针对 COVID-19 住院的 VE 在 Vaxzevria 之间变化范围为 89%（95%CI：52-94）和 mRNA 疫苗的 95%（95%CI：93-97）对于 65-79 岁年龄组，mRNA 疫苗的 VE 为 76%（95%CI：67-83）。对于两种疫苗类型，≥80 岁年龄组的 COVID-19 相关死亡的 VE 均较高，分别为 95%和 81（95%CI：76-86）。我们观察到针对症状感染的 VE 显著下降，对于两种疫苗类型和两组，VE 估计值均接近 34%。在≥80 岁年龄组中，COVID-19 住院的 VE 明显下降（从 mRNA 第二剂后 14-41 天的 83%（95%CI：68-91）下降至 124 天的 63%（95%CI：37-78））。在随访期间，两个队列均未观察到 COVID-19 相关死亡的明显下降效应。
在 SARS-CoV-2 并发症风险较高的人群中，与症状感染相比，我们观察到两个年龄组针对更严重结局的总体 VE 估计值更高。考虑到根据完全接种疫苗后的时间分析 VE，结果显示两个年龄组在症状感染和 80 岁及以上年龄组的 COVID-19 住院方面均出现下降效应。
