Cumulative Incidence of SARS-CoV-2 Infection and Associated Risk Factors Among Frontline Health Care Workers in Paris, France: The SEROCOV Prospective Cohort Study

Abstract

Background: With the COVID-19 pandemic, documenting whether health care workers (HCWs) are at increased risk of SARS-CoV-2 contamination and identifying risk factors is of major concern.Methods: In this multicenter prospective cohort study, HCWs from COVID-19 frontline departments were included in March and April 2020 and followed for 3 months. SARS-CoV-2 serology was performed at month 0 (M0), M1, and M3 and RT-PCR in case of symptoms. The primary outcome was laboratory-confirmed SARS-CoV-2 infection (positive serology and/or positive RT-PCR result) at M3. Secondary outcomes were positive serology for SARS-CoV-2 at M0, M1 and M3. Risk factors of laboratory-confirmed SARS-CoV-2 infection at M3 were identified by multivariate logistic regression.Findings: Among 1,062 HCWs (median [interquartile range] age, 33 [28-42] years; 758 [71.4%] women; 321 [30.2%] physicians), the cumulative incidence of SARS-CoV-2 infection at M3 was 14.6% (95% confidence interval [CI] [12.5; 16.9]). Seroprevalence at M0, M1, and M3 was 5.9% [4.7; 7.5], 12.9% [10.9; 15.1] and 13.0% [11.1; 15.2], respectively. Risk factors were the working department specialty, with increased risk for intensive care units (odds ratio 1.80, 95%CI [0.38; 8.58]), emergency departments (3.91 [0.83; 18.43]) and infectious diseases departments (4.22 [0.92; 18.28]); active smoking was associated with reduced risk (0.36 [0.21; 0.63]). Age, sex, professional category, number of years of experience in the job or department, and public transportation use were not significantly associated with laboratory-confirmed SARS-CoV-2 infection at M3.Interpretation: The rate of SARS-CoV-2 infection in frontline HCWs was 14.6% at the end of the first COVID-19 wave in Paris and occurred mainly early. Seroprevalence in May was higher than in the general population. The study argues for an origin of professional in addition to private life contamination and therefore including HCWs in the first-line vaccination target population. It also highlights that smokers were at lower risk.Trial Registration: The study is registered on ClinicalTrials.gov: NCT04304690Funding Statement: The sponsor of the study was Assistance Publique-Hôpitaux de Paris (AP-HP), with study management by URC Pitié-Salpêtrière. This study was funded by the French Ministry of Health (Programme Hospitalier de Recherche Clinique) and the French Agency for Research (Fond d’amorçage de l’Agence National pour la Recherche).Declaration of Interests: None to declare. Ethics Approval Statement: The SEROCOV study was approved by the ethics committee (CPP Sud-Ouest et Outre-Mer I, approval no. 2-20-023 id7257) and all participants signed informed consent before inclusion.