A phase I trial revealed that UB-612 (a multitope subunit COVID-19 vaccine) exhibits a promising safety profile, effective booster effect against COVID-19 variants of concern (VoCs), and long-lasting B and broad T cell immunity. Chang Yi Wang et al. aimed to report the phase I/II trial findings of a multitope SARS-CoV-2 vaccine in healthy adults.

Overall, 60 young healthy adults (20-55 years of age) were recruited in the phase I primary 2-dose (28 days apart) trial. The recruited volunteers were administered 10, 30, or 100 μg UB-612 vaccine. Out of 60, 50 participants were given 100 μg of UB-612 intramuscularly around 7-9 months following the second dose.

Using two doses of 100 μg of UB-612, a distinct placebo-controlled and randomized phase II study was held in 18-85 years old healthy adults (n = 3,875). Assessment of immunogenicity and interim safety of phase I until fourteen days following the third dose (booster) and of phase II until twenty-eight days following the second dose was carried out.

No vaccine-associated serious side effects were witnessed. Pain at the injection site and fatigue were the frequently observed adverse events, generally short-lived and mild. The vaccine induced neutralizing antibody titers that were comparable to the panel of human convalescent sera in both trials.

The broad T cell immunity against COVID-19 VoCs, long-lasting virus-neutralizing antibodies, and robust booster-recalled memory immunity with elevated cross-reactive neutralizing titers against coronavirus VoCs (Delta and Omicron) were also reported with the use of UB-612 vaccine. Additional advancement of the UB-612 vaccine is warranted for primary immunization effect and heterologous boosting of the other SARS-CoV-2 vaccines.