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Safety and immunogenicity of SARS-CoV-2 vaccine MVC-COV1901 in adolescents in Taiwan: A double-blind, randomized, placebo-controlled phase 2 trial

Background: MVC-COV1901 is a subunit SARS-CoV-2 vaccine based on the prefusion spike protein S-2P and adjuvanted with CpG 1018 and aluminum hydroxide. Although MVC-COV1901 has been licensed for emergency use for adults in Taiwan, the safety and immunogenicity of MVC-COV1901 in adolescents remained unknown. As young people play an important role in SARS-CoV-2 transmission and epidemiology, a vaccine approved for adolescents and eventually, children, will be important in mitigating the COVID-19 pandemic. Methods: This study is a prospective, double-blind, multi-center phase 2 trial evaluating the safety, tolerability and immunogenicity of two doses of the SARS-CoV-2 vaccine MVC-COV1901 in adolescents. Healthy adolescents from age of 12 to 17 years were recruited and randomly assigned (6:1) to receive two intramuscular doses of either MVC-COV1901 or placebo at 28 days apart. The primary outcomes were safety and immunogenicity from the day of first vaccination (Day 1) to 28 days after the second vaccination (Day 57), and immunogenicity of MVC COV1901 in adolescents as compared to young adult vaccinees in terms of neutralizing antibody titers and seroconversion rate. The secondary outcomes were safety and immunogenicity of MVC-COV1901 as compared to placebo in adolescents in terms of immunoglobulin titers and neutralizing antibody titers over the study period. Results: Between July 21, 2021 and December 22, 2021, a total of 399 adolescent participants were included for safety evaluation after enrollment to receive at least one dose of either MVC-COV1901 (N=341) or placebo (N=58). Of these, 334 and 46 participants went on to receive two doses of either MVC-COV1901 or placebo, respectively, and were included in the per protocol set (PPS) for immunogenicity analysis. Adverse events were mostly mild and were similar in MVC-COV1901 and placebo groups. The most commonly reported adverse events were pain/tenderness and malaise/fatigue. All immunogenicity endpoints in the adolescent group were non-inferior to the endpoints seen in the young adult and placebo groups. Conclusions: The safety and immunogenicity data presented here showed that MVC-COV1901 has similar safety profile and non-inferior immunogenicity in adolescents compared to young adults.