Ad26 vaccine protects against SARS-CoV-2 severe clinical disease in hamsters

Coronavirus disease 2019 (COVID-19) in humans is often a clinically mild illness, but some individuals develop severe pneumonia, respiratory failure and death(1-4). Studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in hamsters(5-7)and nonhuman primates(8-10)have generally reported mild clinical disease, and preclinical SARS-CoV-2 vaccine studies have demonstrated reduction of viral replication in the upper and lower respiratory tracts in nonhuman primates(11-13). Here we show that high-dose intranasal SARS-CoV-2 infection in hamsters results in severe clinical disease, including high levels of virus replication in tissues, extensive pneumonia, weight loss and mortality in a subset of animals. A single immunization with an adenovirus serotype 26 vector-based vaccine expressing a stabilized SARS-CoV-2 spike protein elicited binding and neutralizing antibody responses and protected against SARS-CoV-2-induced weight loss, pneumonia and mortality. These data demonstrate vaccine protection against SARS-CoV-2 clinical disease. This model should prove useful for preclinical studies of SARS-CoV-2 vaccines, therapeutics and pathogenesis. A single immunization with an adenovirus vector-based vaccine expressing a stabilized SARS-CoV-2 spike protein induces protection against SARS-CoV-2-induced weight loss, pneumonia and mortality in hamsters.