Immunogenicity and reactogenicity of BNT162b2 booster in ChAdOx1-S-primed participants (CombiVacS): a multicentre, open-label, randomised, controlled, phase 2 trial
Study found that BNT162b2 (Pfizer) given as a second dose in of 676 Spanish subjects prime vaccinated with ChAdOx1-S (Astra Zeneca) induced a robust immune response at day 14, with an acceptable and manageable reactogenicity profile.
Source:
The Lancet
SPS commentary:
The researchers note that this is the first study evaluating the immune and cellular response to a heterologous vaccination strategy against SARS-CoV-2 and confirms previous research suggesting that a heterologous vaccination regimen could elicit potent combined antibody and cellular responses.
A related commentary notes that the study compared this heterologous vaccine regimen to no booster vaccination, but the lack of a homologous vaccination comparator is a major limitation of the study.
It adds that the data are promising in all study participants exhibited neutralising antibodies 14 days after BNT162b2 administration. However, large phase 3 trials including homologous vaccination as a comparator and further observational studies are urgently needed to inform the clinical effectiveness and safety of heterologous regimens in the target populations and settings.