ChAdOx1 nCoV-19 (AZD1222) or nCoV-19-Beta (AZD2816) protect Syrian hamsters against Beta Delta and Omicron variants

Whilst the ChAdOx1 nCoV-19 (AZD1222) vaccine has demonstrated efficacy against symptomatic disease, variants of concern (VOCs) with spike protein substitutions have led researchers to explore updating vaccines from ancestral spike protein. Authors use a Syrian hamster model to evaluate a vaccine encoding the spike protein of Beta VOC and assess efficacy against VOCs. ChAdOx1 nCoV-19 (AZD1222) is a replication-deficient simian adenovirus-vectored vaccine encoding the spike (S) protein of SARS-CoV-2, based on the first published full-length sequence (Wuhan-1). AZD1222 has been shown to have 74% vaccine efficacy against symptomatic disease in clinical trials. However, variants of concern (VoCs) have been detected, with substitutions that are associated with a reduction in virus neutralizing antibody titer. Updating vaccines to include S proteins of VoCs may be beneficial, even though current real-world data is suggesting good efficacy following boosting with vaccines encoding the ancestral S protein. Using the Syrian hamster model, we evaluate the effect of a single dose of AZD2816, encoding the S protein of the Beta VoC, and efficacy of AZD1222/AZD2816 as a heterologous primary series against challenge with the Beta or Delta variant. Minimal to no viral sgRNA could be detected in lungs of vaccinated animals obtained at 3- or 5- days post inoculation, in contrast to lungs of control animals. In Omicron-challenged hamsters, a single dose of AZD2816 or AZD1222 reduced virus shedding. Thus, these vaccination regimens are protective against the Beta, Delta, and Omicron VoCs in the hamster model.

Automated summary

This study evaluates the efficacy of the AZD1222 vaccine and an updated AZD2816 vaccine against variants of concern using a Syrian hamster model. The results show that both vaccines provide protection against the Beta, Delta, and Omicron variants in the hamster model.