Safety and efficacy of RCP recombinant spike protein covid-19 vaccine compared to Sinopharm BBIBP: A phase III, non-inferiority trial

Background: We conducted a phase III, non -inferiority trial comparing safety and efficacy of RCP recombinant spike protein Covid-19 vaccine to BBIBP (Sinopharm). Methods: Adult Iranian population received RCP or BBIBP in a randomized, double blind and an additional non -randomized open labeled trial arms. Eligible participants signed a written informed consent and received two intramuscular injections three weeks apart. In the randomized arm, an intranasal dose of vaccine or adjuvant -only preparation were given to the RCP and BBIBP recipients at day 51 respectively. Participants were actively followed for up to 4 months for safety and efficacy outcomes. Primary outcome was PCR + symptomatic Covid-19 disease two weeks after the second dose. The non -inferiority margin was 10% of reported BBIBP vaccine efficacy (HR = 1.36). Results: We recruited 23,110 participants (7224 in the randomized and 15,886 in the nonrandomized arm). We observed 604 primary outcome events during 4 months of active followup including 121 and 133 in the randomized and 157 and 193 cases in the non -randomized arms among recipients of RCP and BBIBP respectively. Adjusted hazard ratios for the primary outcome in those receiving RCP compared with BBIBP interval were 0.91 (0.71-1.16) and 0.62 (0.49-0.77) in the randomized and non -randomized arms respectively. The upper boundary of 99.1% confidence interval of HR = 0.91 (0.67-1.22) remained below the margin of noninferiority in the randomized arm after observing the early stopping rules using O'Brien Fleming method. Conclusion: Our study showed that the RCP efficacy is non -inferior and its safety profile is comparable to the BBIBP.