NVX-CoV2373 Vaccine Efficacy Against Hospitalization: A post hoc analysis of the PREVENT-19 phase 3, randomized, placebo-controlled trial

PREVENT-19, the pivotal phase 3 trial of the Novavax adjuvanted, recombinant spike protein COVID-19 vaccine (NVX-CoV2373) demonstrated that the vaccine was safe and efficacious (vaccine efficacy, VE= 90%) for the prevention of symptomatic COVID-19. In the trial, participants were randomly assigned in a 2:1 ratio to receive 2 doses of NVX-CoV2373 or placebo 21 days apart. Throughout the study, SARS-CoV-2 circulating variant was predominantly alpha, but other variants circulated (i.e., beta, gamma, epsilon, and iota). VE among the per-protocol efficacy analysis population was calculated according to pre-specified disease severity (mild, moderate, or severe) criteria, but the impact on the risk of COVID-19- associated hospitalization was not specifically investigated. During the placebo-controlled portion of the trial (January 25, 2021, to April 30, 2021), 4 hospitalizations occurred among the 77 events analyzed for the primary endpoint using the per-protocol population, 0 among vaccine recipients and 4 among placebo recipients, yielding a VE against hospitalization of 100% (95% CI: 28.8, 100). Among an expanded efficacy population, which included COVID-19-associated hospitalizations without a requirement for diagnostic polymerase chain reaction testing performed at the study central laboratory, 12 total hospitalizations were identified, 0 among vaccine recipients and 12 among placebo recipients, yielding a post hoc VE against hospitalization of 100% (95% CI: 83.1, 100). These additional data from the PREVENT-19 trial provide relevant public health information concerning the attributes of NVX-CoV2373.