Open label phase I/II clinical trial and predicted efficacy of SARS-CoV-2 RBD protein vaccines SOBERANA 02 and SOBERANA Plus in children

ObjectivesTo evaluate heterologous vaccination scheme in children 3-18 y/o combining two SARS-CoV-2 r-RBD protein vaccines. MethodsA phase I/II open-label, adaptive and multicenter trial evaluated the safety and immunogenicity of two doses of SOBERANA02 and a heterologous third dose of SOBERANA Plus in 350 children 3-18 y/o in Havana Cuba. Primary outcomes were safety (in phase I) and safety/immunogenicity (in phase II) measured by anti-RBD IgG ELISA, molecular and live-virus neutralization titers and specific T-cells response. A comparison with adult s immunogenicity and prediction of efficacy were done based on immunological results ResultsLocal pain was the unique adverse event with frequency >10%, none was serious or severe. Two doses of SOBERANA 02 elicited humoral immune response similar to natural infection; the third dose increased significantly the response in all children, similar to that achieved in vaccinated young adults and higher than in convalescents children. The neutralizing titer was evaluated in a participant s subset: GMT was 173.8 (CI 95% 131.7; 229.5) vs. alpha, 142 (CI 95% 101.3; 198.9) vs. delta and 24.8 (CI 95% 16.8; 36.6) vs. beta. An efficacy > 90% was estimated. ConclusionThe heterologous scheme was safe and immunogenic in children 3-18 y/o. Trial registry: https://rpcec.sld.cu/trials/RPCEC00000374