Phase II/III Study of the AVX/COVID-12 Vaccine Against COVID-19 Applied as a Booster.

This is a phase II/III parallel, double-blind, active-controlled, non-inferiority study to evaluate immunogenicity and safety of a booster immunization scheme of a single intramuscular dose of the recombinant vaccine against SARS-CoV-2 (AVX/COVID-12 vaccine) based on live recombinant Newcastle disease virus (rNDV) vector in healthy adults with a history of vaccination against COVID-19. The study is divided into two phases with immuno-bridging and 3000 healthy subjects showing evidence of prior immunity to SARS-CoV-2 are estimated to enrol. To verify non-inferiority in a determined number of subjects an intramuscular dose of the COVID-19 vaccine (ChAdOx-1-S\[recombinant\]) shall be used as active control in originally randomised subjects. The study shall be carried out in several sites of clinical research in Mexico.