Study of the Humoral Response to SARS-CoV-2 Variants and of the Cellular Response After Vaccination Against COVID-19 in Immunocompromised People

The SARS-CoV-2 pandemic represents an extraordinary challenge for global health, it has caused more than 97 million cases of Covid-19 and 2 million deaths worldwide as of January 22, 2021. Vaccination against Covid-19 is an essential weapon to mitigate the consequences of the SARS-CoV-2 pandemic. Its effect in reducing mortality is of course expected in people most vulnerable to Covid-19 such as immunocompromised people. In general, the immunogenicity of vaccines in immunocompromised populations is conditioned by the nature and intensity of the chronic pathology (s), the age and the treatments received. In addition, the emergence of new variants of SARS-CoV-2 is a major concern today. Three new variants that have rapidly become dominant within their countries have aroused concerns: B.1.1.7 (also known as VOC-202012/01), 501Y.V2 (B.1.351), and P.1 (B.1.1.28.1) and questions are raised about their potential to escape from vaccine-induced immunity. It is therefore important to be able to assess vaccine efficacy in subjects who are fragile with respect to these variants. The investigators are proposing the establishment of a multicenter cohort study of immunocompromised people vaccinated against Covid-19 with the aim to know the humoral and cellular response to BNT162b2 vaccination against SARS-CoV-2 variants. The primary objective is to evaluate the neutralizing capacity of the antibodies regarding different variants of SARS-CoV-2 after vaccination on 1 month after the first injection, then on 1, 6 and 12 months after the last injection. In-depth immunophenotyping of immune blood cells which analyzes in detail the subpopulations of T lymphocytes and their responses to SARS-CoV-2 will be also analyze before vaccination and after vaccination on 1 month after the first injection, then on 1 month after the last injection. Extensive explorations of the humoral and cellular response to BNT162b2 vaccination will provide crucial data on the potential efficacy of the BNT162b2 vaccine on the recently identified SARS-CoV-2 variants, as well as innovative data on the dynamic of the functional responses of T cells and of the TCR repertoire, the dynamic of which (increase after vaccination, remote contraction) makes it possible to link them to a vaccine response, as has already been done in the context of other vaccination. This study will provide a better understanding of the biological response to BNT162b2 vaccination in immunocompromised people with respect to the English VOC 202012/01, South African 501Y.V2 variants and any other variants that may emerge. In particular, the investigators are waiting to be able to estimate the proportion of patients whose immunogenicity suggests a reduction in the frequency of severe forms of COVID-19. Conversely, the investigators are waiting to estimate the proportion of patients with a level of immunogenicity too low to hope for good clinical protection against COVID-19. In addition, there are no data on the durability of the biological response to BNT162b2 vaccination. It is possible that these observations could lead to the implementation of reinforced vaccination protocols for this population, as is already the case for vaccination for hepatitis B vaccination.