Ferrara Pietro, Ponticelli Domenico, Magliuolo Roberto, Borrelli Mario, Schiavone Beniamino, Mantovani Lorenzo Giovanni
Center for Public Health Research, University of Milan-Bicocca, 20900 Monza, Italy.
IRCCS Istituto Auxologico Italiano, 20165 Milan, Italy.
Vaccines (Basel). 2022 Aug 19;10(8):1353. doi: 10.3390/vaccines10081353.
This longitudinal observational study investigated the risk of breakthrough SARS-CoV-2 infection up to 6 months after a booster dose of an mRNA COVID-19 vaccine in infection-naïve vs. previously infected healthcare workers (HCWs), and whether this difference varied over time. A Cox proportional hazard regression model with Aalen's additive analysis was fitted to examine the association between the risk of infections and predictor variables. Overall, we observed an incidence rate of 2.5 cases per 1000 person-days (95% confidence interval [CI] 2.0-3.0), which dropped at 0.8 per 1000 person-days (95% CI 0.3-2.0) in recipients with prior SARS-CoV-2 infection. The fitted analysis indicated an adjusted hazard ratio of 0.32 (95% CI 0.13-0.80; -value = 0.01) for those with hybrid immunity with a slope that became steeply negative roughly starting from day 90. No difference was seen according to participants' smoking habits. Characteristics of infected HCWs were also described. Our study quantifies the time-varying effects of vaccine-induced and hybrid immunity after the booster dose (during the Omicron variant predominance in Italy) and observed that the protection waned more rapidly in infection-naïve recipients starting from the third month. The results add important evidence that can be used to inform COVID-19 vaccination strategies.
这项纵向观察性研究调查了初次感染与既往感染的医护人员在接种一剂新冠病毒mRNA疫苗加强针后长达6个月内出现SARS-CoV-2突破性感染的风险，以及这种差异是否随时间变化。采用带有阿伦累加分析的Cox比例风险回归模型来检验感染风险与预测变量之间的关联。总体而言，我们观察到发病率为每1000人日2.5例（95%置信区间[CI] 2.0 - 3.0），在既往感染过SARS-CoV-2的接种者中降至每1000人日0.8例（95% CI 0.3 - 2.0）。拟合分析表明，具有混合免疫力的人群调整后的风险比为0.32（95% CI 0.13 - 0.80；P值 = 0.01），其斜率大致从第90天开始急剧变为负值。根据参与者的吸烟习惯未观察到差异。还描述了感染医护人员的特征。我们的研究量化了加强针后（在意大利奥密克戎变异株占主导期间）疫苗诱导免疫和混合免疫的随时间变化的影响，并观察到在初次感染的接种者中，从第三个月开始保护作用下降得更快。这些结果为指导新冠病毒疫苗接种策略提供了重要证据。
