Liu X, Shaw RH, Stuart ASV, et al. - The results illustrated that the SARS-CoV-2 anti-spike IgG concentrations of both heterologous schedules were higher than that of a licensed vaccine schedule (ChAd/ChAd) with proven efficacy against COVID-19 disease and hospitalization, despite the BNT/ChAd regimen not meeting non-inferiority criteria. Along with the higher immunogenicity of ChAd/BNT in comparison with ChAD/ChAd, the findings revealed flexibility in the use of heterologous prime-boost vaccination using ChAd and BNT COVID-19 vaccines.

• Researchers enrolled and randomized a total of 830 participants, including 463 participants with a 28-day prime-boost interval, for whom results are reported here.

• In this study, 57·8 years was the mean age of participants (SD 4·7), with 212 (46%) female participants and 117 (25%) from ethnic minorities.

• The geometric mean concentration of SARS-CoV-2 anti-spike IgG in ChAd/BNT recipients (12 906 ELU/mL) was non-inferior to that in ChAd/ChAd recipients (1392 ELU/mL), with a GMR of 9·2 (one-sided 97·5% CI 7·5 to ∞) at day 28 post-boost.

• They did not show non-inferiority of the heterologous schedule (BNT/ChAd, 7133 ELU/mL) against the homologous schedule (BNT/BNT, 14 080 ELU/mL), with a GMR of 0·51 (one-sided 97·5% CI 0·43 to ∞) in participants primed with BNT.

• There were four serious adverse events that occurred across all groups, none of which were considered to be related to immunization.