Neonatal mice immune response to COVID-19 mRNA vaccine

A vaccine based on an mRNA platform was first licensed for human use during the COVID-19 pandemic. However, data on the immunogenicity of SARS-CoV-2 mRNA vaccines in neonates is insufficient and the vaccines were only authorized for those over six months of age. Here, we compared the antibody responses induced by both recombinant receptor binding domain (rRBD) of SARS-CoV-2 spike protein (RBD) and mRNA encoded RBD (RBD-mRNA-LNP) forms in neonatal mice. When administered twice three weeks apart, both forms induced detectable anti-RBD antibodies. However, levels of IgG antibodies against RBD were significantly higher with more potent inhibition of RBD binding to ACE2 in neonatal mice immunized with RBD-mRNA-LNP vaccine compared to those immunized with rRBD vaccine adjuvanted with AddaVax™, a squalene-based adjuvant. Thus, the mRNA vaccine platform elicits higher levels of antibodies with improved functional capability in neonatal mice compared to the recombinant protein platform.