Moderate forms of COVID-19 among healthcare workers in a Belgian hospital and their immune response

Healthcare professionals have been treating patients with COVID-19 since the pandemic started in early 2020 while also trying to limit disease spread among their coworkers and communities. This study aimed to identify and follow potentially infected healthcare workers in one hospital in order to develop an epidemiological baseline for COVID-19 infection and spread rates in this population.

This prospective study was conducted between 1 April and 30 June 2020 at a single Belgian hospital. Healthcare workers with symptoms consistent with COVID-19 were included. Participants underwent testing for SARS-CoV-2 infection by nasopharyngeal (NP) swab and analysis of blood samples for antibody response at different timepoints (day 0, 7, 14 and day 30 or 60). Patient exposures, symptoms, and disease progression were collected.

Of a total of 150 healthcare workers with symptoms compatible with SARS-CoV-2 infection, 31% (47) tested positive for the virus by NP swab. Of the 47 participants with positive NP swabs, 66% also had positive IgG serology. Of the 99 participants with negative NP swabs who underwent blood sample collection, 5% had positive IgG serology results. Of the 29 participants who presented with at least 3 major symptoms, 15 (52%) had positive NP swabs and 14 (48%) had positive serology.

This study demonstrates that evidence of symptoms, even when major, is a poor predictor for SARS-CoV-2 positivity in health care workers and raises the question of the best way to efficiently screen this population especially during the upcoming flu period.