ObjectivesHealthcare workers are more likely to be infected by SARS-CoV-2. In order to assess the infectious risk associated with working in a hospital, we sought to estimate the proportion of healthcare professionals infected with SARS-CoV-2 by screening staff in a University Medical Center in France.SettingA hospital-wide screening campaign (comprising a serological test and a questionnaire) ran from 18 May to 26 July 2020.Primary and secondary outcome measuresThe seroprevalence rate was analysed in a multivariate analysis according to sociodemographic variables (age, sex and profession), exposure to SARS-CoV-2 and symptoms.ResultsA total of 4840 professionals were included, corresponding to 74.5% of the centre’s staff. The seroprevalence rate (95% CI) was 9.7% (7.0% to 12.4%). Contact with a confirmed case of COVID-19 was significantly associated with seropositivity (OR (95% CI: 1.43, (1.15 to 1.78)). The seroprevalence rate was significantly higher among nursing assistants (17.6%) than among other healthcare professionals. The following symptoms were predictive of COVID-19: anosmia (OR (95% CI): 1.55, (1.49 to 1.62)), ageusia (1.21, (1.16 to 1.27)), fever (1.15, (1.12 to 1.18)), myalgia (1.03, (1.01 to 1.06)) and headache (1.03, (1.01 to 1.04)).