An Epidemiological Cohort Study of SARS-CoV-2 and COVID-19 in German Healthcare Workers – Interim Analysis After Six Months of Follow-Up

Background: Healthcare workers (HCWs) are at increased risk of SARS-CoV-2 infection. We followed a large cohort of HCWs in Germany to assess the incidence of SARS-CoV-2 infection and COVID-19 disease before the introduction of COVID-19 vaccines. Methods: We present interim data, collected from August 2020 to January 2021 in the ′CPMprevac′ study, an ongoing prospective observational cohort study including HCWs at the University Medical Centre of Mainz in Germany. Antibody status was assessed at baseline and every 6 weeks (±2 weeks). Daily self-reported COVID-19 symptoms were collected using a smartphone application, and symptomatic HCWs were tested using RT-PCR. We estimated the rates of symptomatic and asymptomatic SARS-CoV-2 infections. The rates of confirmed COVID-19 disease were estimated based on two case definitions of varying sensitivity and specificity. Findings: 3664 HCWs were enrolled in the study with a median follow-up of 101 days. The seroprevalence of anti-SARS-CoV-2 IgM and/or IgG increased from 2·7% at baseline to 3·8%, with the number of seroconversions (65) outweighing seroreversions (26) by the end of follow-up. Among HCWs who seroconverted, 12 (~19%) did not report any symptoms. The incidence rate was estimated to be 4·5 per 1000 person-months. Among the 53 incident cases, none developed severe COVID-19 disease, however, one subject (1·8%) was hospitalized. The most common symptom reported was smell or taste dysfunction, with or without other symptoms. With a median follow up of 100 days, anti-SARS-CoV-2 antibodies fell below diagnostic cut-off value in a third of those positive at baseline and in only one incident case. Interpretation: We observed increasing rates of COVID-19 disease infections among HCWs during a period of accelerated community transmission. The rate of asymptomatic infections, however, was lower than estimates from cross-sectional studies. Nearly one third of seropositive HCWs at baseline reverted by the end of follow-up, however, we did not detect evidence of reinfection. Registration: European Union’s electronic register of Post-Authorisation Studies (EU PAS register number EUPAS37174). Funding: This study was funded by CureVac AG, Tubingen, Germany. Declaration of Interests: Thomas Verstraeten is the managing director of P95, and also a paid consultant at CureVac AG, fulfilling the role of Safety Physician. Stephan Gehring and Frank Kowalzik are employees of UM Mainz and in addition paid for this study as Principal Investigator and Co-Investigator, respectively, by CureVac AG. Omar Okasha, Anirudh Thomer and Wendy Hartig-Merkel are paid employees of P95 and state no conflict of interest. Lidia Oostvogels is a paid employee of CureVac AG. Ethics Approval Statement: The study was approved by the relevant Independent Ethical Committee (IEC; Ethik-Kommission bei der Landesarztekammer Rheinland-Pfalz, Germany).