BACKGROUND Very little is known about the frequency of COVID-19 in health care workers, particularly in developing countries. MATERIALS AND METHODS Cohort study to assess the prevalence of COVID-19 in professionals working in the emergency facilities of five large tertiary hospitals located in Porto Alegre, Southern Brazil (population 1.4 million). Workers were evaluated on July 20-24 (2020), and again after three weeks. At each encounter, clinical data were obtained, and a blood sample was taken by finger pricking for antibody detection (Standard Q COVID-19 IgM/IgG Duo-Biosensor, South Korea). RESULTS Participants (n=1,163) were mostly female (66.6%), and median age was 38 years-old. Close contact with COVID-19 was reported by 82.3%. In the first phase of study, a total of 5.5% (n=64) were found to have antibodies against COVID-19 (26 IgM; 19 IgG; 19 both), including 34.6% (n=27) of workers previously diagnosed with COVID-19 (n=78). After three weeks, seropositivity was 5.6% (17 IgM; 17 IgG; 17 both). IgM and IgG became negative in the second study evaluation for 55.3% and 50.0% of participants who were previously positive for these antibodies, respectively. CONCLUSION This study reveals that a large proportion of health care professionals had been exposed to SARS-CoV-2, developed COVID-19 and presented with antibodies against the disease. For most patients, antibodies disappear over time which may have important implications for the detection of positive cases in epidemiological studies.
Prevalence of coronavirus disease 2019 (COVID-19) among healthcare professionals working in hospital emergencies during the first-wave peak in 2020 in Porto Alegre, Brazil