Sars-COV-2 (COVID-19) Immunity in immunoCOmpromised Populations

Background: In collaboration with several Belgian universities, hospitals and institutes, Sciensano, the Belgian Scientific Institute of Public Health, set up a consortium to facilitate and streamline the organization of COVID-19 vaccination studies primarily in immunocompromised populations. The immune response of COVID-19 vaccination was monitored and studied in the context of the previously PICOV study (P2020/424), Nephro- VAC studies (P2020/284 and P2020/312) and Lung-VAC study (P2021/182). The constant emergence of new variants of concern (VOCs), which become increasingly better at escaping infection and vaccine induced immune responses, together with waning immunity over time, warrant additional vaccination rounds. This is especially true in immunocompromised populations. In the current study, we want to continue monitoring SARS-CoV-2 specific immunity over the next two years, encompassing several future vaccination campaigns. Method: A non-commercial multicenter academic prospective cohort study will be conducted in immunocompromised populations and healthy adults for two years. These healthy people will be recruited from the previously organized PICOV-VAC study (members of nursing home staff) (EudraCT 2021-000401-24) and REDU-VAC study (EudraCT 2021-002088-23) while the immunocompromised participants will be recruited from the previously established PICOV-VAC, REDU-VAC, Lung-VAC and Nephro-VAC cohorts from which historic clinic and immunologic data is available. Participants will be sampled three times a year independently of the vaccinations which will be administered through regular channels not linked to the study itself. Objectives: The main goal of this study is to measure levels of immunity in healthy adults and immunocompromised participants three times a year. The primary objective is to determine binding and neutralizing antibody levels against the epidemiologically predominant SARS- CoV-2 variants of concern (VOC) and the wild type SARS-CoV-2 (Wuhan strain). This will allow us to determine to which extent extra booster doses can or cannot induce more (binding) and/or better (neutralizing) antibodies to different variants as compared to peak responses achieved after previous vaccination doses and to study waning of these responses after winter periods. Secondary objectives include studying the vaccine induced immunity in more detail. This includes the further characterization of the quality of the antibody response and the measurement of the cellular immune response, amongst others.