BBV152/BBV154 Heterologus Prime-Boost Study

All participants will be assessed for immunogenicity and safety endpoints and provide a blood sample before the administration of the first dose of IP. Blood samples will be collected on days 0, 9 (Groups 1, 3 and 4), 28,37 (Groups 2 and 4), 56, 90 and 180 to assess the neutralizing antibody titer against the SARSCoV-2 virus. A subset of 160 Participants (40 participants from each group) will be assessed for immunogenicity analysis, among these subset 10mL of blood and 5mL of saliva will be collected on days 0, 9 (Groups 1, 3 and 4), 28, 37 (Groups 2 and 4), 56, 90 and 180 to assess cell-mediated immunity and mucosal immunogenicity. Group 1 (COVAXIN® + COVAXIN®): In this group, 152 participants will be recruited who will receive COVAXIN® on day 0 and on day 28 via the intramuscular route. Group 2 (COVAXIN® + BBV154): In this group, 152 participants will be recruited who will receive COVAXIN® (Intramuscular) on day 0 and BBV154 (Intranasal) day 28. \*Post 56 days of vaccination, participants with seroconversion rate less than 3 folds will receive another dose of COVAXIN® viaintramuscular route. Group 3 (BBV154 + COVAXIN®): In this group, 152 participants will be recruited who will receive BBV154 (Intranasal) on day 0 and COVAXIN® (Intramuscular) on day 28. \*Post 56 days of vaccination, participants with seroconversion rate less than 3 folds will receive another dose of COVAXIN® via intramuscular route. Group 4 (BBV154 + BBV154): In this group, 152 participants will be recruited who will receive BBV154 on day 0 and on day 28 via the intranasal route.