Data_Sheet_1_The impact of SARS-CoV-2 on healthcare workers of a large University Hospital in the Veneto Region: risk of infection and clinical presentation in relation to different pandemic phases and some relevant determinants.docx

AimThe aim of this study is to evaluate the incidence of SARS-CoV-2 infection and the prevalence of COVID-19-related symptoms in relation to pandemic phases and some relevant variables in a cohort of 8,029 HCWs from one of the largest Italian University Hospitals.
MethodsA single-center retrospective study was performed on data collected during SARS-CoV-2 infection surveillance of HCWs. Cox’s multiple regression was performed to estimate hazard ratios of SARS-CoV-2 infection. Logistic multivariate regression was used to assess the risk of asymptomatic infections and the onset of the most frequent symptoms. All analyses were adjusted for sociodemographic and occupational factors, pandemic phases, vaccination status, and previous infections.
ResultsA total of 3,760 HCWs resulted positive (2.0%–18.6% across five study phases). The total incidence rate of SARS-CoV-2 infection was 7.31 cases per 10,000 person-days, significantly lower in phase 1 and higher in phases 4 and 5, compared to phase 3. Younger HCWs, healthcare personnel, and unvaccinated subjects showed a higher risk of infection. Overall, 24.5% were asymptomatic infections, with a higher probability for men, physicians, and HCWs tested for screening, fully vaccinated, and those with previous infection. The clinical presentation changed over the phases in relation to vaccination status and the emergence of new variants.
ConclusionThe screening activities of HCWs allowed for the early detection of asymptomatic cases, limiting the epidemic clusters inside the hospital wards. SARS-CoV-2 vaccination reduced infections and symptomatic cases, demonstrating again its paramount value as a preventive tool for occupational and public health.

**研究目的**：本研究旨在针对意大利某大型大学附属医院招募的8029名医护人员（Healthcare Workers，HCWs）队列，评估与新冠大流行阶段及相关变量相关的新型冠状病毒（SARS-CoV-2）感染发生率，以及新型冠状病毒肺炎（COVID-19）相关症状的患病率。
**研究方法**：本研究为单中心回顾性研究，分析了医护人员新冠感染监测期间收集的相关数据。采用Cox多元回归模型估算新型冠状病毒感染的风险比；采用多因素Logistic回归模型评估无症状感染风险及最常见症状的发生情况。所有分析均校正了社会人口学因素、职业因素、大流行阶段、疫苗接种状态及既往感染史等混杂变量。
**研究结果**：共计3760名医护人员新冠病毒检测呈阳性，在5个研究阶段中阳性率介于2.0%~18.6%之间。新型冠状病毒感染的总发生率为7.31例/10000人日，与第3阶段相比，第1阶段感染率显著更低，第4、5阶段感染率显著更高。年轻医护人员、普通医护人员及未接种疫苗者感染风险更高。总体而言，24.5%的感染为无症状感染，男性、医师、接受筛查检测的医护人员、完全接种疫苗者及有既往感染史者出现无症状感染的概率更高。不同大流行阶段的临床表型随疫苗接种状态及新变异株的出现而发生变化。
**研究结论**：医护人员的筛查工作可实现无症状感染者的早期发现，从而限制医院病房内的聚集性疫情。新型冠状病毒疫苗接种可降低感染及有症状病例的发生风险，再次证明其作为职业健康与公共卫生预防工具的极高价值。