Safety and Immunogenicity of SW-BIC-213, a Modified COVID-19 Lipo-Polyplex mRNA Vaccine, in Laotian Healthy Adults Aged 18 Years and Above: A Phase 1/2 Trial

Background/Objectives: Messenger RNA vaccines can induce strong immune responses, but delivery, biodistribution, and storage stability remain important considerations. We evaluated the safety and immunogenicity of SW-BIC-213, a Lipo-Polyplex (LPP)-based mRNA vaccine against SARS-CoV-2, in healthy adults in Laos. Methods: We conducted a seamless phase 1/2 clinical trial in healthy adults. Phase 1 enrolled adults aged 18–60 years in an open-label, single-arm dose-escalation study; phase 2 enrolled adults aged ≥18 years in a randomized, double-blind, placebo-controlled study. Participants received two doses 21 days apart. The primary endpoints were safety in phase 1 and safety and immunogenicity in phase 2. Results: In phase 1, 41 participants received 25 or 45 μg of SW-BIC-213. In phase 2, 480 participants were randomized in a 2:2:1 ratio to receive 25 μg, 45 μg, or placebo. All phase 1 adverse reactions were grade 1 or 2; grade 3 reactions in phase 2 were limited to transient fever. At 14 days after the second dose, pseudovirus neutralizing-antibody seroconversion exceeded 99% against wild-type virus, 98% against Delta, 84% against Omicron BA.1, and 88% against BA.2. Neutralizing-antibody titers were higher in both vaccine groups than in the placebo group (p < 0.0001). Conclusions: Two doses of SW-BIC-213 showed an acceptable safety profile and substantial humoral immunogenicity in healthy adults aged ≥18 years.