mRNA-1273.261

mRNA-1273.261 is an investigational, variant-containing mRNA vaccine candidate developed by Moderna for the prevention of COVID-19. As part of the mRNA-1273 (Spikevax) platform, it consists of lipid nanoparticle (LNP)-encapsulated messenger RNA that encodes a specific version of the SARS-CoV-2 spike (S) protein, likely corresponding to a then-emergent variant. The vaccine works by delivering the mRNA into host cells, which then translate the genetic sequence into the spike protein, triggering an immune response including the production of neutralizing antibodies and T-cell activation. It has been evaluated in Phase 3b/4 clinical trials in the European Union to assess its safety and immunogenicity against vaccine-matched and newly emerged SARS-CoV-2 variants in previously vaccinated populations.