PROS1 and COVID-19: The entry of rVSV-SARS-CoV-2 and rVSV-SARS-CoV is mediated by the heterogenous S proteins engaging the major cellular receptor ACE2.35 Immunohistochemical analysis revealed that there are significant higher levels of ACE2 in the respiratory tract than in skeletal muscle tissues.40 Furthermore, the nasal tissue is highly susceptible to SARS-CoV-2,41 suggesting that the i.n. route might be more suitable for administration of VSV-based COVID-19 vaccine than the i.m. route.