ABNCoV2 Vaccine in Adult Subjects Previously Vaccinated for SARS-CoV-2

This trial is composed of a randomized, double-blind, active controlled component (Part A) and an open-label, single-arm component (Part B) conducted in parallel. Part A is designed to compare vaccination with a single 100 µg dose of ABNCoV2 to a single 30 µg adult booster dose of Comirnaty (active control) in adult subjects who either previously completed primary vaccination (Cohort 1) or have already received 1 booster dose (Cohort 2) of SARS-CoV-2 locally authorized vaccine(s), and whose last locally authorized SARS-CoV-2 vaccination was at least 3 months prior to the screening visit. Subjects will be randomized in a 1:1 ratio to receive either ABNCoV2 or Comirnaty. Part B is designed to collect ABNCoV2 safety and tolerability data from a larger population of adult subjects, as well as additional immunogenicity data from a subset. Part B involves vaccination with the same single 100 µg dose of ABNCoV2 in the same population of adult subjects as the randomized component, and subjects will similarly be enrolled into 2 cohorts according to whether they have completed primary vaccination only or primary plus booster vaccination.