immunogenic(1) COVID-19(1) elicit(1) COVID-19 vaccine(1) delta variant(1) Beta(1) nucleocapsid antigen(1) Safe(1) healthy volunteers(1) Wuhan-Hu-1(1) Efficacy(1) SARS-CoV-2 variant(1) response(1) Protective(1) Lower respiratory tract(1) weight loss(1) clinical investigation(1) immunology(1) evade(1) Virology(1) immunization(1) hamster(1) cross-protective immunity(1) cross-reactive antibody(1) neutralizing antibody responses(1) PROTECT(1) Vaccine(1) Infection(1) vaccine candidate(1) intramuscular(1)