ABSTRACT mRNA vaccines are one of the most promising vaccine platforms available to rapidly deploy in response to emerging viral infections. However, the duration of the protective antibody response induced by these vaccines is limited, even after multiple vaccine doses. The rapid decay of the antibody response to mRNA vaccines necessitates frequent revaccinations. The immunogenicity of vaccines based on conventional mRNA may be reduced due to triggering TLR 3, 7 and 8, and RIG-I receptors resulting in strong induction of the innate immune response. This leads to expression and activation of protein kinase R and 2’-5’-oligoadenylate synthetase, which in turn leads to suppression of translation. As circular RNA does not have termini, it stimulates innate immune responses weaker. Moreover, circular RNA has the advantage of prolonged expression due to resistance to exonucleases. A protein produced from circular RNA is detectable in serum or at a site of injection for a much longer period of time as compared to linear mRNA. Extended antigen availability to mimic the natural kinetics of antigen delivery during viral infections has shown to be highly effective in potentiating germinal center responses to immunogens. Hantaviruses are globally emerging pathogens; the New World hantaviruses Andes virus (ANDV) and Sin Nombre virus cause hantavirus cardiopulmonary syndrome with a case fatality rate up to 40%. A recent outbreak of ANDV demonstrated transmission through direct contact with infected individuals but also airborne human-to-human, highlighting the significant pandemic potential of this virus. The proposal is based on extensive preliminary data which show that ANDV linear mRNA vaccine platforms are protective against ANDV challenge in the 100% lethal hamster model. The proposal is aimed at testing the hypothesis that the innovative circular RNA vaccine construct against ANDV will elicit the most potent adaptive immune response including diversity and magnitude of