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Summary Objectives Risk of reinfection with SARS-CoV-2 among health-care workers (HCWs) is unknown. We assessed the incidence rate of SARS-CoV-2 reinfection in the real-life setting of a longitudinal observational cohort of HCWs from the Hopital Europeen Georges Pompidou, Assistance Publique-Hopitaux de Paris, France, during the first and second waves of COVID-19 epidemic. Methods From March to December 2020, HCWs were subjected to molecular and serology testing of SARS-CoV-2. Reinfection was defined as a positive test result during the first wave, either by serology or PCR, followed by a positive PCR during the second wave. Evolution of COVID-19 status of HWCs was assessed by a Sankey diagram. Results A total of 7765 tests (4579 PCR and 3186 serology) were carried out and 4168 HCWs had at least one test result during the follow-up period with a positivity rate of 15.9%. No case of reinfection during the second wave could be observed among 102 positive HCWs of the first wave, nor among 175 HCWs found positive by PCR during the second wave who were negative during the first wave. Conclusions SARS-CoV-2 reinfection was not observed among HCWs, suggesting a protective immunity against reinfection that lasts at least 8 months post infection.

Highlights • The average SARS-CoV-2 seroprevalence in healthcare workers of a a tertiary hospital, University Hospital Essen, Germany was 1.6% in the period between March to April 2020. • The local hygiene standards seem to be effective to prevent patient-to-staff virus transmission at the designated COVID-19 units wards., Background The novel coronavirus SARS-CoV-2 is associated with a severe respiratory manifestation, COVID-19, and presents a challenge for healthcare systems worldwide. Healthcare workers are a vulnerable cohort for SARS-CoV-2 infection due to frequent and close contact to patients with COVID-19. Study design Serum samples from 316 healthcare workers of the University Hospital Essen, Germany were tested for SARS-CoV-2-IgG antibodies. A questionnaire was used to collect demographic and clinical data. Healthcare workers were grouped depending on the frequency of contact to COVID-19 patients in high-risk-group (n = 244) with daily contact to known or suspected SARS-CoV-2 positive patients, intermediated-risk-group (n = 37) with daily contact to patients without known or suspected SARS-CoV-2 infection at admission and low-risk-group (n = 35) without patient contact. Results In 5 of 316 (1.6%) healthcare workers SARS-CoV-2-IgG antibodies could be detected. The seroprevalence was higher in the intermediate-risk-group vs. high-risk-group vs. 2/37 (5.4%) vs. (3/244 (1.2%), p = 0.13). Four of the five subject were tested negative for SARS-CoV-2 via PCR. One (20%) subject was not tested via PCR since he was asymptomatic. Conclusion The overall seroprevalence of SARS-CoV-2 in healthcare workers of a tertiary hospital in Germany is low (1.6%). The data indicate that the local hygiene standard might be effective.