Materials and methods
MAY, SECONDARY
This was a Phase 3, multicentric, non-inferiority, observer-blinded, randomized, active controlled study in adults who had completed primary immunization with either ChAdOx1 nCoV-19 or BBV152 at least 6 months ago. A total of 372 eligible participants were enrolled in two prime cohorts of 186 participants each with 1:1 allocation to SII-NVX-CoV2373 or control vaccine. The study was conducted from May 2022 to December 2022 at 8 hospitals in India. The study was registered on Clinical Trials Registry-India (CTRI/2022/04/042017).The primary objective was to demonstrate non-inferiority of the SII-NVX-CoV2373 heterologous booster against the homologous booster of control vaccine using anti-S IgG and neutralizing antibodies (nAbs) for ChAdOx1 nCoV-19, and BBV152 Prime cohorts, separately. The secondary objective was to assess the tolerability and reactogenicity profile of SII-NVX-CoV2373 booster in comparison with the control vaccine. As an exploratory objective, the study also assessed immune responses by nAbs, anti-S IgG and human ACE2 (hACE2) receptor binding inhibition assays against variants of concern (VoC).