Characterization of the SARS-CoV-2 BA.5.5 and BQ.1.1 Omicron Variants in Mice and Hamsters.

As SARS-CoV-2 continues to evolve, there is a need to rapidly assess the efficacy of vaccines and antiviral therapeutics against newly emergent variants. To do so, the commonly used animal models must also be reevaluated. Here, we determined the pathogenicity of the circulating BQ.1.1 SARS-CoV-2 variant in multiple SARS-CoV-2 animal models including transgenic mice expressing human ACE2, two strains of conventional laboratory mice, and Syrian hamsters. While BQ.1.1 infection resulted in similar levels of viral burden and clinical disease in the conventional laboratory mice tested, increases in lung infection were detected in human ACE2-expressing transgenic mice, which corresponded with greater levels of pro-inflammatory cytokines and lung pathology. Moreover, we observed a trend towards greater animal-to-animal transmission of BQ.1.1 than BA.5.5 in Syrian hamsters. Together, our data highlight important differences in two closely related Omicron SARS-CoV-2 variant strains and provide a foundation for evaluating countermeasures.