A single-dose mRNA vaccine provides a long-term protection for hACE2 transgenic mice from SARS-CoV-2

A long-term efficacy of SARS-CoV-2 mRNA vaccine was evaluated by using hACE2 Tg mice. The mRNA vaccine is desinged to express the receptor-binding domain (RBD) of spike (S) protein of SARS-CoV-2 strain HB-01, containing the modified nucleoside N1-methylpseudouridine to prevent innate immune sensing and increase mRNA translation. This is partially different from that of Pfizer, whose mRNA vaccine encodes full-length S.  Wild type mice were immunized with the RBD-encoding mRNA vaccine, and 6.5 months later, the sera were transferred to hACE2 Tg mice. In this case, the sera-transferred Tg mice showed near perfect protection against the challenge infection of SARS-CoV-2. These data suggests that the single imunization of mRNA vaccine can elicit neutralizing antibodies that persist for long-term (6.5 months for mice).