SARS-CoV-2 Prevalence and Seroprevalence among Healthcare Workers in Belgian Hospitals: Baseline Results of a Prospective Cohort Study

Abstract

Background: Given the current SARS-CoV-2 pandemic and the occurrence of a second wave, assessing the burden of disease among health care workers (HCWs) is crucial. We aim to document the prevalence of SARS-CoV-2 and the seroprevalence of anti-SARS-CoV-2 IgG among HCWs in Belgian hospitals, and to study potential risk factors for the infection in order to guide infection prevention and control (IPC) measures in healthcare institutions. Methods: We performed a cross-sectional analysis of the baseline results (April 22 - April 26) of an ongoing cohort study. All staff who were present in the hospital during the sampling period and whose profession involved contact with patients were eligible. Fourteen hospitals across Belgium and 50 HCW per hospital were randomly selected. RT-qPCR was performed to detect SARS-CoV-2 RNA on nasopharyngeal swabs, and a semi-quantitative IgG ELISA was used to detect anti-SARS-CoV-2 antibodies in sera. Individual characteristics likely to be associated with seropositivity were collected using an online questionnaire. Findings: 698 participants completed the questionnaire; 80.8% were women, median age was 39.5, and 58.5% were nurses. Samples were collected on all 699 participants. The weighted anti-SARS-CoV-2 IgG seroprevalence was 7.7% (95%CI, 4.7%-12.2%), while 1.1% (95%CI, 0.4%-3.0%) of PCR results were positive. Unprotected contact with a confirmed case was the only factor associated with seropositivity (PR 2.16, 95% CI, 1.4-3.2). Interpretation: Most Belgian HCW did not show evidence of SARS-CoV-2 infection by late April 2020, and unprotected contact was the most important risk factor. This confirms the importance of widespread availability of protective equipment and use of adequate IPC measures in hospital settings.

Prospective SARS-CoV-2 cohort study among general practitioners during the second COVID-19 wave in Flanders, Belgium

“…The cohort of participants represents a convenience sample of PHCPs, mainly GPs (n=641), women (n=520) and a mean age of 41.1 years (SD=11.6) (Table 1). The seroprevalence of PHCPs after the first COVID-19 wave was 4.6% (95%CI 3.2-6.4%) in June, which is in line with the seroprevalence of blood donors (4.9%; 95%CI 3.1-5.9%), (9) but lower than the seroprevalence of hospital HCWs (9.4%; 95%CI 6.5-13.4%) (11) at that time in Flanders. The seroprevalence of PHCPs remained stable until September, but increased significantly from October to December to 13.4% (95%CI 10.8-16.4%).…”

Age-dependent seroprevalence of SARS-CoV-2 antibodies in school-aged children from areas with low and high community transmission

“…The overall seroprevalence among children in our study was higher than expected compared to international reports and compared to seroprevalence studies in health care workers and blood donors in Belgium, including samples collected in the same region [1][2][3][8][9][10][11][12]. For example, 4.5% (95% CI: 0.2%-21.5%) seropositivity was found in residual samples of 0-to 10-year olds and 7.2% (95% CI 1.1%-21.6%) in 10-to 20-year olds in the province Limburg [10].…”

Persistence of IgG response to SARS-CoV-2

“…Participants are tested on a monthly basis for the presence of SARS-CoV-2 with quantitative RT-PCR (RT-qPCR) and for antibodies targeting S1 (spike subunit 1) protein with a commercial semi-quantitative ELISA (Euroimmun IgG; Medizinische Labordiagnostika, Lübeck, Germany), using a stringent manufacturer-defined cut-off for having a positive test result (ratio ≥1·1; NCT04373889 ). 6 By the end of September, 2020, seven rounds of testing had been done. To assess the longevity of the humoral immune response, we recorded the duration of the presence of detectable IgG in the serum of health-care workers who were seropositive for SARS-CoV-2.…”