Comparative Immunogenicity of the Gam-COVID-Vac Vaccine under Intranasal and Intramuscular Administration

In this work, we set out to compare the immunogenicity of the Gam-COVID-Vac two-component vaccine produced by GENERIUM JSC (Russia) following its intranasal or intramuscular administration of the first or both components to BALB/c mice. The immunogenicity was evaluated according to antigen-specific IgG and IgA antibodies in the blood and bronchoalveolar fluid, the number of antigen-specific IFN-γ-producing T-lymphocytes, the number of antigen-specific IFN-γ-producing CD4 and CD8 T-lymphocytes. Intranasal administration was shown to induce the mucosal immunity, significantly exceeding both qualitatively and quantitatively the effect of intramuscular administration (by the number of animals with antigen-specific IgA antibodies and the titer of antibodies in blood serum and bronchoalveolar lavage). At the same time, intramuscular administration slightly exceeded the effect obtained under intranasal administration in terms of the total number of CD8-IFN-γ-producing lymphocytes.