A Phase 1 Study to Assess the Safety and Immunogenicity of JCXH-221, an MRNA-based Broadly Protective COVID-19 Vaccine

The goal of this clinical trial is to learn about, test, and compare JCXH-221 in healthy volunteers. The main aims to answer are: * To assess the safety and tolerability of the JCXH-221 vaccine in healthy adult subjects * To identify an optimal dose for the JCXH-221 vaccine in healthy adult subjects * To assess the humoral immunogenicity of the JCXH-221 vaccine in healthy adult subjects * To characterize the cellular immunogenicity of the JCXH-221 vaccine in healthy adult subjects Participants for Phase I will be randomized to either JCXH-221 or placebo.