Efficacy of ChAdOx1 vaccines against SARS-CoV-2 variants of concern Beta, Delta and Omicron in the Syrian hamster model

Preprint

ChAdOx1 nCoV-19 (AZD1222) is a replication-deficient simian adenovirusâ€"vectored vaccine encoding the spike (S) protein of SARS-CoV-2, based on the first published full-length sequence (Wuhan-1). AZD1222 was shown to have 74% vaccine efficacy (VE) against symptomatic disease in clinical trials and over 2.5 billion doses of vaccine have been released for worldwide use. However, SARS-CoV-2 continues to circulate and consequently, variants of concern (VoCs) have been detected, with substitutions in the S protein that are associated with a reduction in virus neutralizing antibody titer. Updating vaccines to include S proteins of VoCs may be beneficial over boosting with vaccines encoding the ancestral S protein, even though current real-world data is suggesting good efficacy against hospitalization and death following boosting with vaccines encoding the ancestral S protein. Using the Syrian hamster model, we evaluated 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. We then investigated the efficacy of a single dose of AZD2816 or AZD1222 against the Omicron VoC. As seen previously, minimal to no viral sgRNA could be detected in lungs of vaccinated animals obtained at 5 days post inoculation, in contrast to lungs of control animals. Thus, these vaccination regimens are protective against the Beta, Delta, and Omicron VoCs in the hamster model.

Authors: van Doremalen, N; Schulz, JE; Adney, DR; Saturday, TA; Fischer, RJ

• Publication status: Published
• Peer review status: Not peer reviewed
• Preprint server: Research Square
• Place of publication: United States
• Publication date: 2022-02-15
• DOI: 10.21203/rs.3.rs-1343927/v1
• EISSN: 2693-5015
• Pmid: 35194602
• Server owner: Research Square Company
• Language: English