 Altimmune Inc NASDAQ: ALT has announced positive results from a preclinical study evaluating its intranasal COVID-19 vaccine candidate, AdCOVID, in a SARS-CoV-2 challenge model of infection. The results showed that a single dose of AdCOVID provided sterilizing immunity in the lungs of vaccinated mice, in contrast to the development of dense pulmonary infection and disease in the lungs of non-vaccinated mice following infection with SARS-CoV-2. 