They performed a phase 2, open-label, randomised, controlled trial on adults aged 18–60 years, vaccinated with a single dose of Vaxzevria® vaccine 8–12 weeks before screening, and no history of previous SARS-CoV-2 infection.
Participants were randomly assigned (2:1) to receive either Comirnaty® COVID-19 Vaccine (0·3 mL) via a single intramuscular injection (intervention group) or continue observation (control group). The control group did not routinely receive a second dose of Vaxzevria®, but it could be used if requested by the participant or established by local health authorities.
The primary outcome was 14-day immunogenicity, measured by immunoassays for SARS-CoV-2 trimeric spike protein and receptor binding domain (RBD). The safety outcome was 7-day reactogenicity, measured as solicited local and systemic adverse events.
663 (98%) participants (n=441 intervention, n=222 control) completed the study up to day 14.
In the intervention group, the mean antibody levels increased from 71·46 BAU/mL.
Reactions were mild (n=1210 [68%]) or moderate (n=530 [30%]), with injection site pain (n=395 [88%]), induration (n=159 [35%]), headache (n=199 [44%]), and myalgia (n=194 [43%]) the most commonly reported adverse events. No serious adverse events were reported.
Comirnaty® given as a second dose in individuals prime vaccinated with Vaxzevria® induced a robust immune response, with an acceptable and manageable reactogenicity profile.
Borobia AM A et al
The Lancet. VOLUME 398, ISSUE 10295, P121-130. ; DOI: https://doi.org/10.1016/S0140-6736(21)01420-3