A Phase 1/2 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 subjectsTo identify an optimal dose for the JCXH-221 vaccine in healthy adult subjectsTo assess the humoral immunogenicity of the JCXH-221 vaccine in healthy adult subjectsTo characterize the cellular immunogenicity of the JCXH-221 vaccine in healthy adult subjectsParticipants for Phase I will be randomized to either JCXH-221 or placebo. In Phase 2, participants will be randomized to either JCXH-221 or a FDA approved Active comparator.

Main Inclusion CriteriaSex: Male or female; female subjects may be of childbearing potential, of nonchildbearing potential, or postmenopausal.Age: 18 years of age or older, at screening.Status: Healthy subjects.Subjects must have completed the full doses for primary vaccination with an approved SARS-CoV-2 vaccine and may have received booster dose(s), with the last vaccination (can be 2nd dose of primary vaccination or booster dose) having occurred at least 4 months prior to enrollment.Main Exclusion CriteriaCurrent or prior symptomatic or asymptomatic SARS-CoV-2 infection confirmed by an approved or authorized rapid antigen test on Day 1 or within 4 months prior to Day 1.Subjects with significant exposure (as defined by current CDC guidance) to someone with laboratory confirmed SARS-CoV-2 infection or COVID-19 with the past 14 days prior to the Screening visit.Subjects with fever or signs of acute infection at the time of enrollment and vaccination.Subjects who are taking medications that may prevent or treat COVID-19.Subjects who received convalescent serum or prior therapeutic antibodies against SARS-CoV-2 within 4 months before Day 1.Subjects with history of myocarditis or pericarditis, or with AEs after mRNA vaccination that are in nature and severity beyond the common AEs expected and necessitating medical intervention.Subjects with active or suspected immunosuppression, immunodeficiency, or autoimmune disease.