Liu X, Shaw RH, Stuart ASV, et al. - Findings from this first participant-blinded randomized clinical trial using two vaccines approved by WHO for emergency use, ChAd and BNT, support their safety and immunogenicity when administered at a 28-day interval in heterologous and homologous vaccine schedules (ChAd/ChAd, ChAd/BNT, BNT/BNT, and BNT/ChAd).

• In this participant-blinded, randomized, non-inferiority trial, participants were administered ChAd/ChAd, ChAd/BNT, BNT/BNT, or BNT/ChAd, at either 28-day or 84-day prime-boost intervals.

• The BNT/ChAd regimen did not meet non-inferiority criteria.

• However, there were higher SARS-CoV-2 anti-spike IgG concentrations of both heterologous schedules relative to that of a licensed vaccine schedule (ChAd/ChAd) with proven efficacy against COVID-19 disease and hospitalization.

• The data revealed a higher immunogenicity of ChAd/BNT vs ChAD/ChAd, as well as support flexibility in the use of heterologous prime-boost vaccination using ChAd and BNT COVID-19 vaccines.