SARS-CoV-2 Seroprevalence among Healthcare Workers after the First and Second Pandemic Waves.

Background: The Grand Hôpital de Charleroi is a large non-academic Belgian hospital that treated a large number of COVID-19 inpatients. In the context of this pandemic, all professions-combined healthcare workers (HCWs), and not only direct caregivers, are a frontline workforce in contact with suspected and confirmed COVID-19 cases and seem to be a high-risk group for exposure. The aim of our study was to estimate the prevalence of anti-SARS-CoV-2 antibodies in HCWs in our hospital after the first and second pandemic waves and to characterize the distribution of this seroprevalence in relation to various criteria. Methods: At the end of the two recruitment periods, a total of 4008 serological tests were performed in this single-center cross-sectional study. After completing a questionnaire including demographic and personal data, possible previous COVID-19 diagnostic test results and/or the presence of symptoms potentially related to COVID-19, the study participants underwent blood sampling and serological testing using DiaSorin's LIAISON® SARS-CoV-2 S1/S2 IgG test for the first phase and LIAISON® SARS-CoV-2 TrimericS IgG test for the second phase of this study. Results: In total, 302 study participants (10.72%) in the first round of the study and 404 (33.92%) in the second round were positive for SARS-CoV-2-IgG antibodies. The prevalence of seropositivity observed after the second wave was 3.16 times higher than after the first wave. We confirmed that direct, prolonged, and repeated contact with patients or their environment was a predominant seroconversion factor, but more unexpectedly, that this was the case for all HCWs and not only caregivers. Finally, the notion of high-risk contact seemed more readily identifiable in one's workplace than in one's private life. Conclusions: Our study confirmed that HCWs are at a significantly higher risk of contracting COVID-19 than the general population, and suggests that repeated contacts with at-risk patients, regardless of the HCWs' professions, represents the most important risk factor for seroconversion (Clinicaltrials.gov number, NCT04723290).

Monitoring of human coronaviruses in Belgian primary care and hospitals, 2015-20: a surveillance study.

BACKGROUND: Seasonal human coronaviruses (hCoVs) broadly circulate in humans. Their epidemiology and effect on the spread of emerging coronaviruses has been neglected thus far. We aimed to elucidate the epidemiology and burden of disease of seasonal hCoVs OC43, NL63, and 229E in patients in primary care and hospitals in Belgium between 2015 and 2020. METHODS: We retrospectively analysed data from the national influenza surveillance networks in Belgium during the winter seasons of 2015-20. Respiratory specimens were collected through the severe acute respiratory infection (SARI) and the influenza-like illness networks from patients with acute respiratory illness with onset within the previous 10 days, with measured or reported fever of 38°C or greater, cough, or dyspnoea; and for patients admitted to hospital for at least one night. Potential risk factors were recorded and patients who were admitted to hospital were followed up for the occurrence of complications or death for the length of their hospital stay. All samples were analysed by multiplex quantitative RT-PCRs for respiratory viruses, including seasonal hCoVs OC43, NL63, and 229E. We estimated the prevalence and incidence of seasonal hCoV infection, with or without co-infection with other respiratory viruses. We evaluated the association between co-infections and potential risk factors with complications or death in patients admitted to hospital with seasonal hCoV infections by age group. Samples received from week 8, 2020, were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). FINDINGS: 2573 primary care and 6494 hospital samples were included in the study. 161 (6·3%) of 2573 patients in primary care and 371 (5·7%) of 6494 patients admitted to hospital were infected with a seasonal hCoV. OC43 was the seasonal hCoV with the highest prevalence across age groups and highest incidence in children admitted to hospital who were younger than 5 years (incidence 9·0 [95% CI 7·2-11·2] per 100 000 person-months) and adults older than 65 years (2·6 [2·1-3·2] per 100 000 person-months). Among 262 patients admitted to hospital with seasonal hCoV infection and with complete information on potential risk factors, 66 (73·3%) of 90 patients who had complications or died also had at least one potential risk factor (p=0·0064). Complications in children younger than 5 years were associated with co-infection (24 [36·4%] of 66; p=0·017), and in teenagers and adults (≥15 years), more complications arose in patients with a single hCoV infection (49 [45·0%] of 109; p=0·0097). In early 2020, the Belgian SARI surveillance detected the first SARS-CoV-2-positive sample concomitantly with the first confirmed COVID-19 case with no travel history to China. INTERPRETATION: The main burden of severe seasonal hCoV infection lies with children younger than 5 years with co-infections and adults aged 65 years and older with pre-existing comorbidities. These age and patient groups should be targeted for enhanced observation when in medical care and in possible future vaccination strategies, and co-infections in children younger than 5 years should be considered during diagnosis and treatment. Our findings support the use of national influenza surveillance systems for seasonal hCoV monitoring and early detection, and monitoring of emerging coronaviruses such as SARS-CoV-2. FUNDING: Belgian Federal Public Service Health, Food Chain Safety, and Environment; Belgian National Insurance Health Care (Institut national d'assurance maladie-invalidité/Rijksinstituut voor ziekte-en invaliditeitsverzekering); and Regional Health Authorities (Flanders Agentschap zorg en gezondheid, Brussels Commission communautaire commune, Wallonia Agence pour une vie de qualité).

Impact of solid cancer on in-hospital mortality overall and among different subgroups of patients with COVID-19: a nationwide, population-based analysis.

BACKGROUND: Cancer seems to have an independent adverse prognostic effect on COVID-19-related mortality, but uncertainty exists regarding its effect across different patient subgroups. We report a population-based analysis of patients hospitalised with COVID-19 with prior or current solid cancer versus those without cancer. METHODS: We analysed data of adult patients registered until 24 May 2020 in the Belgian nationwide database of Sciensano. The primary objective was in-hospital mortality within 30 days of COVID-19 diagnosis among patients with solid cancer versus patients without cancer. Severe event occurrence, a composite of intensive care unit admission, invasive ventilation and/or death, was a secondary objective. These endpoints were analysed across different patient subgroups. Multivariable logistic regression models were used to analyse the association between cancer and clinical characteristics (baseline analysis) and the effect of cancer on in-hospital mortality and on severe event occurrence, adjusting for clinical characteristics (in-hospital analysis). RESULTS: A total of 13 594 patients (of whom 1187 with solid cancer (8.7%)) were evaluable for the baseline analysis and 10 486 (892 with solid cancer (8.5%)) for the in-hospital analysis. Patients with cancer were older and presented with less symptoms/signs and lung imaging alterations. The 30-day in-hospital mortality was higher in patients with solid cancer compared with patients without cancer (31.7% vs 20.0%, respectively; adjusted OR (aOR) 1.34; 95% CI 1.13 to 1.58). The aOR was 3.84 (95% CI 1.94 to 7.59) among younger patients (<60 years) and 2.27 (95% CI 1.41 to 3.64) among patients without other comorbidities. Severe event occurrence was similar in both groups (36.7% vs 28.8%; aOR 1.10; 95% CI 0.95 to 1.29). CONCLUSIONS: This population-based analysis demonstrates that solid cancer is an independent adverse prognostic factor for in-hospital mortality among patients with COVID-19. This adverse effect was more pronounced among younger patients and those without other comorbidities. Patients with solid cancer should be prioritised in vaccination campaigns and in tailored containment measurements.