Immune responses against SARS-CoV-2 variants after heterologous and homologous ChAdOx1 nCoV-19/BNT162b2 vaccination

In a study of healthcare professionals previously vaccinated with ChAdOx-1 nCoV-19, booster vaccination with BNT162b2 elicited more neutralizing antibodies with greater breadth, as well as higher frequencies of virus-specific T cells, than ChAdOx-1 nCoV-19. Currently approved viral vector-based and mRNA-based vaccine approaches against coronavirus disease 2019 (COVID-19) consider only homologous prime-boost vaccination. After reports of thromboembolic events, several European governments recommended using AstraZeneca's ChAdOx1-nCov-19 (ChAd) only in individuals older than 60 years, leaving millions of already ChAd-primed individuals with the decision to receive either a second shot of ChAd or a heterologous boost with mRNA-based vaccines. However, such combinations have not been tested so far. We used Hannover Medical School's COVID-19 Contact Study cohort of healthcare professionals to monitor ChAd-primed immune responses before and 3 weeks after booster with ChAd (n = 32) or BioNTech/Pfizer's BNT162b2 (n = 55). Although both vaccines boosted prime-induced immunity, BNT162b2 induced significantly higher frequencies of spike-specific CD4(+) and CD8(+) T cells and, in particular, high titers of neutralizing antibodies against the B.1.1.7, B.1.351 and P.1 variants of concern of severe acute respiratory syndrome coronavirus 2.

Automated summary

A study found that booster vaccination with BNT162b2 in healthcare professionals previously vaccinated with ChAdOx-1 nCoV-19 elicited more neutralizing antibodies and higher frequencies of virus-specific T cells. Additionally, BNT162b2 induced high titers of neutralizing antibodies against variants of concern, such as B.1.1.7, B.1.351, and P.1.