SARS-CoV-2 seroprevalence in healthcare workers of a teaching hospital in a highly endemic region in the Netherlands after the first wave: a cross-sectional study

OBJECTIVE: To study the SARS-CoV-2 infection rate among hospital healthcare workers after the first wave of the COVID-19 pandemic, and provide more knowledge in the understanding of the relationship between infection, symptomatology and source of infection. DESIGN: A cross-sectional study in healthcare workers. SETTING: Northern Limburg, the Netherlands. PARTICIPANTS: All employees of VieCuri Medical Center (n=3300) were invited to enrol in current study. In total 2507 healthcare workers participated. INTERVENTION: Between 22 June 2020 and 3 July 2020, participants provided venous blood samples voluntarily, which were tested for SARS-CoV-2 antibodies with the Wantai SARS-CoV-2 Ig total ELISA test. Work characteristics, exposure risks and prior symptoms consistent with COVID-19 were gathered through a survey. MAIN OUTCOME MEASURE: Proportion of healthcare workers with positive SARS-CoV-2 serology. RESULTS: The overall seroprevalence was 21.1% (n=530/2507). Healthcare workers between 17 and 30 years were more likely to have SARS-CoV-2 antibodies compared with participants >30 years. The probability of having SARS-CoV-2 antibodies was comparable for healthcare workers with and without direct patient (OR 1.42, 95% CI 0.86 to 2.34) and COVID-19 patient contact (OR 1.62, 95% CI 0.80 to 3.33). On the contrary, exposure to COVID-19 positive coworkers (OR 1.83, 95% CI 1.15 to 2.93) and household members (OR 6.09, 95% CI 2.23 to 16.64) was associated with seropositivity. Of those healthcare workers with SARS-CoV-2 antibodies, 16% (n=85/530) had not experienced any prior COVID-19-related symptoms. Only fever and anosmia were associated with seropositivity (OR 1.90, 95% CI 1.42 to 2.55 and OR 10.51, 95% CI 7.86 to 14.07). CONCLUSIONS: Healthcare workers caring for hospitalised COVID-19 patients were not at an increased risk of infection, most likely as a result of taking standard infection control measures into consideration. These data show that compliance with infection control measures is essential to control secondary transmission and constrain the spread of the virus.