Description of the studied population (N = 710).

The emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the subsequent coronavirus disease 2019 (COVID-19) pandemic with the continuous evolution of the virus into variants such as Alpha, Beta, Delta, Omicron and others necessitates an on-going surveillance and evaluation of vaccine effectiveness (VE).This study focuses on assessing the real-world performance of the Pfizer-BioNTech (BNT162b2) vaccine against the Omicron variant. This study employs a test-negative, case-control design, a methodology commonly utilized for estimating the VE in influenza studies. It evaluates SARS-CoV-2 test results in individuals aged 50 and older who had influenza-like illness (ILI) or COVID-like illness (CLI) symptoms and presented to the sentinel sites, classifying positive cases as “cases” and negative as “controls.” Data collection was done through a standardized questionnaire administered by the Epidemiological Surveillance Unit (ESU) COVID-19 team via phone interviews. Logistic regression analysis was performed to measure the association, taking into account all confounding factors. The results indicate a 14% VE against contracting the disease among fully vaccinated individuals. Factors such as age and underlying conditions significantly influenced VE. The findings of this study highlight the effectiveness of the Pfizer-BioNTech (BNT162b2) vaccine in reducing the odds of symptomatic COVID-19, particularly by decreasing the prevalence of key symptoms such as fever, cough, myalgia, and loss of taste or smell. Breakthrough infections still occurred, indicating that while the vaccine reduces symptom severity, it may not fully prevent infection This VE is lower compared to previous variants, indicating potential challenges in vaccine efficacy. The study underscores the need for an on-going monitoring and potential booster doses to enhance protection, especially against evolving variants like Omicron.

新型严重急性呼吸综合征冠状病毒2（SARS-CoV-2）的出现，以及随之而来的2019冠状病毒病（COVID-19）大流行，且该病毒持续进化出阿尔法（Alpha）、贝塔（Beta）、德尔塔（Delta）、奥密克戎（Omicron）等变异株，使得对疫苗有效性（VE）开展持续监测与评估成为必要。本研究聚焦于评估辉瑞-生物泰克（BNT162b2）疫苗针对奥密克戎变异株的真实世界防护效果。本研究采用检测阴性病例对照研究设计——这也是流感疫苗有效性评估研究中常用的方法学手段——对50岁及以上、出现流感样病例（ILI）或新冠样病例（CLI）症状并前往哨点监测点就诊的人群的SARS-CoV-2检测结果进行分析，将检测阳性者归类为“病例组”，检测阴性者归类为“对照组”。数据收集由流行病学监测组（ESU）新冠疫情工作组通过电话访谈，采用标准化问卷完成。研究采用logistic回归分析，校正所有混杂因素后评估疫苗与感染结局的关联强度。结果显示，全程接种疫苗的个体对有症状感染的疫苗有效性为14%。年龄与基础疾病等因素对疫苗有效性存在显著影响。本研究结果表明，辉瑞-生物泰克（BNT162b2）疫苗可降低有症状新冠病毒感染的发生风险，尤其能减少发热、咳嗽、肌痛以及味觉或嗅觉丧失等核心症状的发生频率。尽管仍有突破性感染发生，提示该疫苗虽可减轻症状严重程度，但无法完全阻断感染；且本次评估的疫苗有效性较既往变异株更低，提示针对奥密克戎等不断进化的变异株，疫苗防护面临潜在挑战。本研究强调，需持续开展监测并考虑接种加强针以提升防护效果，尤其是针对持续进化的新冠变异株。