SARS-CoV-2 infection prevention and control measures in Belgian schools between December 2020 and June 2021 and their association with seroprevalence: a cross-sectional analysis of a prospective cohort study.

BACKGROUND: To protect school-aged children from the potential consequences of a new viral infection, public health authorities recommended to implement infection prevention and control (IPC) measures in school settings. Few studies evaluated the implementation of these measures and their effect on SARS-CoV-2 infection rates among pupils and staff. The aim of this study was to describe the implementation of infection prevention and control (IPC) measures in Belgian schools and assess its relation to the prevalence of anti-SARS-CoV-2 antibodies among pupils and staff. METHODS: We conducted a prospective cohort study in a representative sample of primary and secondary schools in Belgium between December 2020 and June 2021. The implementation of IPC measures in schools was assessed using a questionnaire. Schools were classified according to their compliance with the implementation of IPC measures as 'poor', 'moderate' or 'thorough'. Saliva samples were collected from pupils and staff to determine the SARS-CoV-2 seroprevalence. To assess the association between the strength of implementation of IPC measures and SARS-CoV-2 seroprevalence among pupils and staff, we conducted a cross-sectional analysis using the data collected in December 2020/January 2021. RESULTS: A variety of IPC measures (ventilation, hygiene and physical distancing) was implemented by more than 60% of schools, with most attention placed on hygiene measures. In January 2021, poor implementation of IPC measures was associated with an increase in anti-SARS-CoV-2 antibody prevalence among pupils from 8.6% (95%CI: 4.5 - 16.6) to 16.7% (95%CI: 10.2 - 27.4) and staff from 11.5% (95%CI: 8.1 - 16.4) to 17.6% (95%CI: 11.5 - 27.0). This association was only statistically significant for the assessment of all IPC measures together in the population comprised of pupils and staff. CONCLUSIONS: Belgian schools were relatively compliant with recommended IPC measures at the school level. Higher SARS-CoV-2 seroprevalence among pupils and staff was found in schools with poor implementation of IPC measures, compared to schools with thorough implementation. TRIAL REGISTRATION: This trial is registered under the NCT04613817 ClinicalTrials.gov Identifier on November 3, 2020.

SARS-CoV-2 seroprevalence and determinants for salivary seropositivity among pupils and school staff: a prospective cohort study.

Representative school data on SARS-CoV-2 past-infection are scarce, and differences between pupils and staff remain ambiguous. We performed a nation-wide prospective seroprevalence study among pupils and staff over time and in relation to determinants of infection using Poisson regression and generalised estimating equations. A cluster random sample was selected with allocation by region and sociodemographic (SES) background. Surveys and saliva samples were collected in December 2020, March, and June 2021, and also in October and December 2021 for primary pupils. We recruited 885 primary and 569 secondary pupils and 799 staff in 84 schools. Cumulative seroprevalence (95% CI) among primary pupils increased from 11.0% (7.6; 15.9) at baseline to 60.4% (53.4; 68.3) in December 2021. Group estimates were similar at baseline; however, in June they were significantly higher among primary staff (38.9% (32.5; 46.4)) compared to pupils and secondary staff (24.2% (20.3; 28.8)). Infections were asymptomatic in 48-56% of pupils and 28% of staff. Seropositivity was associated with individual SES in pupils, and with school level, school SES and language network in staff in June. Associations with behavioural characteristics were inconsistent. Seroconversion rates increased two- to four-fold after self-reported high-risk contacts, especially with adults. Seroprevalence studies using non-invasive sampling can inform public health management.

COVID-19 Clusters in Belgian Nursing Homes: Impact of Facility Characteristics and Vaccination on Cluster Occurrence, Duration and Severity.

COVID-19 severely affected nursing home residents from March 2020 onwards in Belgium. This study aimed to model the impact of vaccination and facility characteristics on cluster occurrence, duration and severity in this setting. Possible clusters were identified between June 2020 and January 2022, based on the Belgian COVID-19 surveillance in nursing homes. Median attack rates (AR) among residents and staff, case hospitalization rates (CHR) and case fatality rates (CFR) were calculated. A negative binomial model was used to identify the association between nursing home characteristics and the number of cases, hospital admissions and deaths and the duration of the cluster. A total of 2239 clusters were detected in more than 80% of nursing homes. Most of these (62%) occurred before the start of COVID-19 vaccination (end of December 2020). After vaccination, the number of clusters, the AR among residents and staff, the CHR and the CFR dropped. Previous cluster(s) and vaccination decreased the number of cases, hospital admissions and deaths among residents. Previous cluster experience and having started vaccination were protective factors. We recommend continued implementation of targeted interventions such as vaccination, large-scale screening and immediate implementation of additional infection prevention and control measures.

Effect of COVID-19 Vaccination Campaign in Belgian Nursing Homes on COVID-19 Cases, Hospital Admissions, and Deaths among Residents.

In view of the grave situation during the first two waves of SARS-CoV-2 virus (severe acute respiratory syndrome coronavirus-2), nursing homes (NHs) were prioritised for vaccination once vaccines became available in Belgium. The aim of this study was to assess the effect of the COVID-19 (Coronavirus Disease 2019) vaccination campaign on COVID-19 cases, hospital admissions, and deaths among residents living in Belgian NHs. All 1545 Belgian NHs were invited to participate in a COVID-19 surveillance program. In Belgium, before vaccination, COVID-19 morbidity and mortality rates were driven by the situation in the NHs. Shortly after the COVID-19 vaccination campaign, and later the booster campaign, the number of hospital admissions and deaths among NH residents dropped, while clear peaks could be observed among the general population. The impact of vaccination on virus circulation was less effective than expected. However, due to the high vaccination coverage, NH residents remain well protected against hospital admission and death due to COVID-19 more than one year after being vaccinated.

COVID-19 cases, hospitalizations and deaths in Belgian nursing homes: results of a surveillance conducted between April and December 2020.

BACKGROUND: In Belgium, the first COVID-19 death was reported on 10 March 2020. Nursing home (NH) residents are particularly vulnerable for COVID-19, making it essential to follow-up the spread of COVID-19 in this setting. This manuscript describes the methodology of surveillance and epidemiology of COVID-19 cases, hospitalizations and deaths in Belgian NHs. METHODS: A COVID-19 surveillance in all Belgian NHs (n = 1542) was set up by the regional health authorities and Sciensano. Aggregated data on possible/confirmed COVID-19 cases and hospitalizations and case-based data on deaths were reported by NHs at least once a week. The study period covered April-December 2020. Weekly incidence/prevalence data were calculated per 1000 residents or staff members. RESULTS: This surveillance has been launched within 14 days after the first COVID-19 death in Belgium. Automatic data cleaning was installed using different validation rules. More than 99% of NHs participated at least once, with a median weekly participation rate of 95%. The cumulative incidence of possible/confirmed COVID-19 cases among residents was 206/1000 in the first wave and 367/1000 in the second wave. Most NHs (82%) reported cases in both waves and 74% registered ≥10 possible/confirmed cases among residents at one point in time. In 51% of NHs, at least 10% of staff was absent due to COVID-19 at one point. Between 11 March 2020 and 3 January 2021, 11,329 COVID-19 deaths among NH residents were reported, comprising 57% of all COVID-19 deaths in Belgium in that period. CONCLUSIONS: This surveillance was crucial in mapping COVID-19 in this vulnerable setting and guiding public health interventions, despite limitations of aggregated data and necessary changes in protocol over time. Belgian NHs were severely hit by COVID-19 with many fatal cases. The measure of not allowing visitors, implemented in the beginning of the pandemic, could not avoid the spread of SARS-CoV-2 in the NHs during the first wave. The virus was probably often introduced by staff. Once the virus was introduced, it was difficult to prevent healthcare-associated outbreaks. Although, in contrast to the first wave, personal protective equipment was available in the second wave, again a high number of cases were reported.