SPECC1 and infection: In the hamster infection model, the two resistant viruses were slightly attenuated, maintained airborne transmissibility with slightly reduced efficiency, and were unable to compete with the growth of the wild-type virus in the absence of nirmatrelvir; however, although Nsp5-L50F/E166V was dominated by the wild-type virus in the nasal turbinate in the presence of the drug, it dominated in three of five animals in the lungs.