COVID-19 vaccine mRNA-1273 elicits a protective immune profile in mice that is not associated with vaccine-enhanced disease upon SARS=CoV-2 challenge

Immunization of mice with COVID-19 vaccine mRNA-1273 reduced viral titers in the lung without a remarkable pathogenic change after mouse-adapted SARS-CoV-2 challenge. This vaccination induced both cellular and humoral immune responses. In contrast, immunization with whole-inactivated virion or heat-denatured spike protein sub-unit vaccines elicited humoral immune responses, which reduced viral titers but induced severe pathological changes in the lung. This resembles a vaccine-associated enhanced respiratory disease observed in the infection of SARS-CoV-1 and MERS coronavirus.