Distinct Innate Immune Responses Following Inoculation With a Replicon mRNA COVID-19 Vaccine.

Innate immune responses trigger the development of adaptive immune responses through the production of cytokines. In the present study, we compared the cytokine production in mice inoculated with a novel replicon mRNA COVID-19 vaccine. Biphasic and prolonged IFN-γ production was observed after the first dose, and sustained production was observed after the second dose, whereas conventional mRNA vaccines induced a peak of IFN-γ production only on Day 1 after both first and second inoculations. These findings may be associated with the self-replicating properties of the replicon mRNA vaccine following inoculation.