Participants received a single intramuscular injection of vaccine or placebo in the arm and were monitored for 30 minutes post-injection for adverse drug reactions (ADRs). Follow-up visits occurred at 14 days, 28 days, and 6 months post-vaccination to assess specific antibody responses, neutralizing antibody responses, and other safety/immunogenicity endpoints. Participants self-reported adverse events (ADEs) throughout the study for documentation. Blood samples were drawn on the day of vaccination and at 14 and 28 days post-vaccination to measure specific antibody responses against the receptor-binding domain via ELISA. Neutralizing antibody and cellular immune responses were measured before vaccination and 28 days after: cellular immune response via ELISpot assay for interferon-γ, and neutralizing antibody response via a serum neutralization assay.