SARS-CoV-2 serostatus of healthcare worker in the Austrian state Vorarlberg between June 2020 and January 2021

BackgroundAustria, and particularly its westernmost federal state Vorarlberg, developed the highest COVID-19 incidence rate worldwide in November 2020. Health care workers (HCW) may be at higher risk of contracting the disease within the working environment and therefore the seroprevalence in this population is of particular interest. Here, we analyzed SARS-CoV-2-specific antibody response in Vorarlberg HCW in a prospective cohort study. MethodsA total of 395 HCW have been tested at three different time points for the prevalence of anti-SARS-CoV-2 IgG antibodies specific for NP and RBD. Enrollment started in June 2020 (t1), two months after the end of the first wave. Re-testing took place between October to November at the beginning of the second wave (t2), and again at the end of the second wave in January 2021(t3). ResultsAt t1, 3% of HCW showed a strong IgG-specific responses to either NP or RBD. At t2, the rate increased to 4%, and after the second wave in January 2021, 14% had a strong response, which was assessed to be stable for up to ten months. The amount of HCW with anti-SARS-CoV-2 IgG antibodies was 38% higher than the number of infections found by PCR. ConclusionWe found low numbers of SARS-CoV-2-seropositive HCW in a hotspot setting after the first wave but a massive increase during the second wave distinctly surpassing the number of infected HCW identified by PCR. Our findings, therefore, offer support for the routine application of serological testing in management of the ongoing COVID-19 pandemic. Main summaryA relatively low percentage of 3% SARS-CoV-2 seropositive HCW with strong IgG-specific antibody responses was found in the Austrian federal state Vorarlberg after the first wave increasing to 14% after the second massive wave lasting until January 2021.