Abstract
Abstract Seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG antibodies, using dried blood spots, was determined in October–November 2020, among residents and staff randomly selected from 20 nursing homes (NH) geographically distributed in Flanders, Belgium. Sociodemographic and medical data [including coronavirus disease 2019 (COVID-19) symptoms and results of RT-PCR tests] were retrieved using questionnaires. The overall seroprevalence was 17.1% [95% confidence interval (CI) 14.9–19.5], with 18.9% (95% CI 15.9–22.2) of the residents and 14.9% (95% CI 11.9–18.4) of the staff having antibodies, which was higher than the seroprevalence in blood donors. The seroprevalence in the 20 NH varied between 0.0% and 45.0%. Fourteen per cent of the staff with antibodies, reported no typical COVID-19 symptoms, while in residents, 51.0% of those with antibodies had no symptoms. The generalised mixed effect model showed a positive association between COVID-19 symptoms and positive serology, but this relation was weaker in residents compared to staff. This study shows that NH are more affected by SARS-CoV-2 than the general population. The large variation between NH, suggests that some risk factors for the spread among residents and staff may be related to the NH. Further, the results suggest that infected people, without the typical COVID-19 symptoms, might play a role in outbreaks.
Highlights
Worldwide, Belgium was one of the countries with the highest number of coronavirus disease 2019 (COVID-19) deaths per capita [1]
After investigating the relation between the variable ‘staff versus resident’ and serology result, we explored the relation between the serology and the self-reported RT-PCR results and self-reported manifestation of COVID-19 symptoms
The correlation of serological results with sociodemographic variables was based on complete cases for serology results and questionnaire data and modelling was assessed on the subset of 998 participants, where a self-reported RT-PCR test result was available
Summary
Belgium was one of the countries with the highest number of coronavirus disease 2019 (COVID-19) deaths per capita [1]. In Europe, the WHO estimated that at the end of June 2020, about half of the COVID-19 deaths were NH residents [3]. Seroprevalence data have been published from the general Belgian population, primary health care workers and more recently from school children and staff [4]. The available results [4, 5], revealed that, the percentage of blood donors (as a proxy for the general Belgian population) with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies was increasing from 5.0% (end of April 2020) up to 9.2% by the end of October 2020. For hospital staff [4, 6, 7], the seroprevalence was varying between 7.7% (end of April 2020) and 10.8% (end of October 2020)
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