Mix and Match Heterologous Prime-Boost Study Using Approved COVID-19 Vaccines

This is a phase 2, observer-blind, randomized study to assess the safety and the immunogenicity of heterologous prime-boost COVID-19 vaccines regimens in healthy adults aged 18 to 65 years using two approved vaccines (Sinopharm / CNBG Vaccine (BBIBP-CorV) and Johnson \& Johnson Vaccine (Ad26.COV2.S)). The study will consist of 2 cohorts, one for main immunology endpoints (N=260, 65 per study arm) and one for more detailed immunological assessment (N=100, 25 per study arm). Two doses of vaccine will be administered intramuscularly 4 week apart. All the study participants will be follow-up for 12 months from the administration of first vaccine dose.