Centre for Infectious Disease Control, National Institute for Public Health and Environment (RIVM), Bilthoven, the Netherlands.
Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht (UMCU), Utrecht, the Netherlands.
Int J Infect Dis. 2023 Aug;133:36-42. doi: 10.1016/j.ijid.2023.04.401. Epub 2023 Apr 20.
We estimated vaccine effectiveness (VE) of primary and booster vaccinations against SARS-CoV-2 infection overall and in four risk groups defined by age and medical risk condition during the Delta and Omicron BA.1/BA.2 periods.
VAccine Study COvid-19 is an ongoing prospective cohort study among Dutch adults. The primary end point was a self-reported positive SARS-CoV-2 test from July 12, 2021 to June 06, 2022. The analyses included only participants without a previous SARS-CoV-2 infection based on a positive test or serology. We used Cox proportional hazard models with vaccination status as the time-varying exposure and adjustment for age, sex, educational level, and medical risk condition.
A total of 37,170 participants (mean age 57 years) were included. In the Delta period, VE <6 weeks after the primary vaccination was 80% (95% confidence interval 69-87) and decreased to 71% (65-77) after 6 months. VE increased to 96% (86-99) shortly after the first booster vaccination. In the Omicron period, these estimates were 46% (22-63), 25% (8-39), and 57% (52-62), respectively. For the Omicron period, an interaction term between vaccination status and risk group significantly improved the model (P <0.001), with generally lower VEs for those with a medical risk condition.
Our results show the benefit of booster vaccinations against infection, also in risk groups; although, the additional protection wanes quite rapidly.
我们评估了针对 Delta 和 Omicron BA.1/BA.2 变异株期间，年龄和医疗风险状况定义的四个风险组中，SARS-CoV-2 感染的初级和加强疫苗接种的总体有效性（VE）。
VAccine Study COvid-19 是一项正在进行的荷兰成年人前瞻性队列研究。主要终点是 2021 年 7 月 12 日至 2022 年 6 月 6 日期间自我报告的 SARS-CoV-2 阳性检测。分析仅包括基于阳性检测或血清学的先前 SARS-CoV-2 感染的参与者。我们使用 Cox 比例风险模型，将疫苗接种状态作为随时间变化的暴露因素，并调整年龄、性别、教育水平和医疗风险状况。
共纳入 37170 名参与者（平均年龄 57 岁）。在 Delta 期间，初级接种后 6 周内 VE 为 80%（95%置信区间 69-87），6 个月后降至 71%（65-77）。在第一次加强接种后不久，VE 增加到 96%（86-99）。在 Omicron 期间，这些估计值分别为 46%（22-63）、25%（8-39）和 57%（52-62）。对于 Omicron 期间，疫苗接种状态和风险组之间的交互项显著改善了模型（P <0.001），具有医疗风险状况的个体的 VE 通常较低。
我们的结果表明加强疫苗接种对感染具有保护作用，在风险组中也是如此；然而，额外的保护作用迅速减弱。
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