Monitoring SARS-CoV-2-specific immunity upon COVID-19 vaccination in nursing home residents and staff

Nearly 60% of all COVID-19 deaths in Belgium so far were nursing home (NH) residents. Therefore, in January 2021, Belgium prioritised NH residents and staff for vaccination with the Pfizer-BioNTech (PB) vaccine in the COVID-19 vaccination campaign. The PB vaccine showed 95% efficacy in a phase III trial, but older people were largely underrepresented. This is worrisome, since older adults most often suffer from immunosenescence (decreased immunity), frailty and comorbidities, all of which are strongly related with decreased responses upon vaccination targeting other infections. Additionally, it is unclear whether COVID-19 vaccination will offer sufficient protection against the emerging SARS-CoV-2 variants of concern. Therefore, our overall aim is to monitor PB-vaccine induced immune responses and clinical protectiveness in nursing home residents and staff. The proposal is embedded within a large-scale national COVID-19 epidemiological study in nursing homes that started in February 2021. In NH residents and staff, we aim (i) to use capillary blood collected on paper cards (ie. dried blood spots), currently being collected, to monitor the level of neutralising antibodies; (ii) to evaluate the level of protection after vaccination against the emerging SARS-CoV-2 variants in real-time using in-house pseudoneutralisation assays; (iii) to document incident COVID-19 cases and correlate these with antibody levels and to (iv) investigate cellular immunity in non-responders.