A Double-blind, Randomized, Controlled, Phase 2a Study to Evaluate the Safety and Tolerability of a Newcastle Disease Virus-based Mucosal Vaccine (NDV-HXP-S-KP.2) Relative to an Approved Systemic mRNA Vaccine in Previously Vaccinated Adults

Inclusion Criteria: 1. Is an adult 18 through 64 years of age at time of screening with at least 1 underlying condition that puts the participant at high risk for severe outcomes of COVID-19 per self-report OR is an adult ≥65 years of age at time of screening (with or without at least 1 underlying condition). 2. Has completed any WHO/FDA-authorized or approved primary COVID-19 vaccination series per self-report. 3. Has received last COVID-19 vaccine ≥6 months prior to study vaccination. 4. If a female of childbearing potential who is sexually active, agrees to use an adequate method of birth…