SARS-CoV-2 seroprevalence in high-risk health care workers in a Belgian general hospital: evolution from the first wave to the second.

Health care workers (HCWs) are at the frontline for combatting the ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. To describe recent or past infections, the novel development of serological assays enabled the assessment of the immune response developed in coronavirus disease (COVID-19). Here, we investigate SARS-CoV-2 seroprevalence in high-risk HCWs in a Belgian general hospital after both the first and the second waves. Three different immunoassays were used to determine immune response to SARS-CoV-2 in volunteer HCWs who worked in at least one COVID-19-dedicated ward [emergency department, intensive care unit (ICU) and internal medicine department] in our institution from 8 May 2020 to 19 May 2020 (n = 267) and from 18 January 2021 to 8 February 2021 (n = 189). Risk factors for seropositivity were also assessed using a questionnaire filled out by all participants. We report a steep increase in seroprevalence after the second wave and report a higher seropositivity in HCWs than in the general population. Furthermore, we show that ICU personnel and especially nurses exhibit a proportionally lower SARS-CoV-2 seroprevalence. This study documents the rapid increase in SARS-CoV-2 seroprevalence in highly exposed HCWs in a context of high viral circulation prior to vaccination campaigns. Most importantly, it suggests a lower occupational risk in ICU and illustrates the role of diagnostic labeling and use of personal protective equipment during the COVID-19 pandemic.