A randomized trial comparing safety, immunogenicity and efficacy of self-amplifying mRNA and adenovirus-vector COVID-19 vaccines
Nhan Thi Ho, Steven G. Hughes, Rose E. Sekulovich, Van Thanh Ta, Thượng Vũ Nguyễn, Anh Thi Van Pham, Quang Chấn Lương, Lydia Tran, Anh Thi Luu, Anh Ngọc Nguyễn, Hong Thi Thuy Pham, Van Thu Nguyen, Dina Berdieva, Roberto Bugarini, Xuexuan Liu, Carole Verhoeven, Igor Smolenov, Xuan‐Hung Nguyen
Abstract
This phase 3 trial compared safety, tolerability, immunogenicity and efficacy of the self-amplifying mRNA COVID-19 vaccine, ARCT-154, with ChAdOx1-S adenovirus-vector vaccine. In four centers in Vietnam adult participants aged 18‒85 years were randomly assigned to receive two doses, 28 days apart, of either ARCT-154 (n = 1186) or ChAdOx1-S (n = 1180). Both vaccines were well tolerated with similar safety and reactogenicity profiles consisting of mainly mild-to-moderate solicited adverse events and few related serious adverse events. Higher neutralizing antibody responses persisting to one-year post-vaccination after ARCT-154 compared with ChAdOx1-S were associated with a generally higher efficacy against COVID-19. In an exploratory analysis relative vaccine efficacy of ARCT-154 vs. ChAdOx1-S against any COVID-19 from Day 36 to Day 394 was 19.8% (95% CI: 4.0-33.0). Self-amplifying mRNA vaccine offers potential immunological advantages in terms of immunogenicity and efficacy over adenovirus-vector vaccine without compromising safety.