Real-word immunogenicity of a recombinant subunit COVID-19 vaccine and effectiveness against omicron infection: a prospective, multi-centre, longitudinal cohort study in Alzheimer's disease patients

Introduction Vaccination is an essential strategy against COVID-19 in the current era of emerging variants. This study evaluates the real-world immunogenicity and effectiveness of the recombinant subunit COVID-19 vaccine (Zifivax) in Alzheimer's disease (AD) patients. Methods 249 AD patients were enrolled in a multicentre, longitudinal cohort study. Levels of RBD-IgG, neutralization antibody activity, and cytokines were identified to evaluate the immune responses. Clinical outcomes were assessed within one month following Omicron infection.. Results Following three doses, the vaccine induced a robust immune response, elevating neutralizing antibodies and activating T-cells. AD patients exhibited significantly higher humoral immune responses compared to unvaccinated counterparts. Following Omicron infection, unvaccinated patients experienced higher levels of Th1/Th2-type cytokines than vaccinated individuals. Vaccination correlated with increased survival rates and extended survival times after infection.. Discussion The findings highlight the vaccine's efficacy in reducing severe illness, and preventing death in AD patients facing Omicron infection.