The mRNA-1273 vaccine, developed by Moderna, is an mRNA-based COVID-19 vaccine formulated with lipid nanoparticles to deliver the mRNA encoding the spike protein antigen of SARS-CoV-2, eliciting an immune response. It has shown about 94% efficacy in preventing COVID-19 after two doses and provides significant protection against various strains, including Alpha, Beta, Delta, and Omicron.