Assessing Immune Response of Different COVID-19 Vaccines in Older Adults

This is a randomised controlled, adaptive, multicentre Phase II protocol evaluating different booster strategies in individuals aged 75 years and older already vaccinated against SARS-CoV-2. Part A of this trial foresees testing of different vaccines as a 3rd vaccination dose (first booster) for comparative assessment of their immunogenicity and safety against SARS-CoV-2 wild-type and variants in the elderly, a usually neglected population. Part B of this trial foresees testing of different vaccines as a 4th vaccination dose (second booster) for comparative assessment of their immunogenicity and safety against SARSCoV-2 wild-type and variants in the identical population.