Safety, and Immunogenicity Study of the Recombinant Two-component COVID-19 Vaccine (CHO Cell)

Overview

Part 1: Primary Vaccination in Adults Part 1 will evaluate the safety and immunogenicity of the recombinant two component COVID-19 vaccine (CHO cell) (ReCOV for short) in adults aged 18 years and older, when administered as 2 intramuscular doses, 21 days apart. Part 2: Booster Vaccination in Adults Part 2 will evaluate the immunogenicity and safety and of one booster dose of ReCOV in adult participants who have received primary vaccination with 2 doses of an inactivated COVID-19 vaccine (CoronaVac®). COMIRNATY®, an mRNA COVID-19 vaccine will be used as the active control.

Part 1: Primary Vaccination in Adults Around 340 participants aged 18 years and older who do not have known COVID-19 or COVID-19 vaccination history will be randomized into ReCOV group (40 μg) or placebo group in a ratio of 2:1. Accordingly, around 227 participants will receive 40 μg ReCOV and 113 participants will receive matching placebo, respectively. Participants will be stratified by age (18\~59 years, ≥60 years) and status of SARS-CoV-2 antibody at baseline. After randomization, participants will enter into a double-blinded period (until all participants complete V6) and an open-label long-term follow-up period (after all participants complete V6 until end of the study). After all participants complete the visit at 7 days after the 2nd vaccination, the safety and reactogenicity data will be summarized by an independent statistic group, while the sponsor, investigators and all study participants will be kept blinded. The safety summary will be submitted to DSMB for review and recommendation on the initiation of Part 2. The primary analysis of Part 1 is planned after all participants complete the Visit 6 (V3 + 28 days, +7 days) and are unblinded, to evaluate the safety and immunogenicity during the double-blinded period. The final analysis of Part 1 will be conducted after all participants of the ReCOV group complete the follow-up visit at 6 months after the 2nd vaccination, to evaluate the safety and immunogenicity during this study stage. Part 2: Booster Vaccination in Adults This study part will enroll participants who have received primary vaccination by an inactivated COVID-19 vaccine (CoronaVac®) within 3 to 12 months (90\~365 days). The mRNA COVID-19 vaccine, COMIRNATY ®, will be used as the active control. The immunogenicity induced by the booster vaccination of ReCOV (commercial batch, Lot# TC202205002) will be compared with that of COMIRNATY®. In addition, the immunogenicity of one dose booster of commercial batch ReCOV (Lot# TC202205002) will be compared with that of pilot batch ReCOV (Lot# HA202107009). About 600 participants will be enrolled into the study. Eligible participants will be 1:1:1 randomized to receive 20 μg ReCOV (Lot# HA202107009), 20 μg ReCOV (Lot# TC202205002), or 30 μg COMIRNATY®, stratified by age (18\~59 years, ≥60 years) and the duration since the last primary vaccination (90\~180 days, 181\~365 days). All participants will be followed up for safety and reactogenicity. Participants will be observed for 30 minutes at study site after the vaccination. Before leaving the study site, participants will be given participant diaries to record solicited AEs within 7 days after dosing, and unsolicited AEs within 28 days after dosing. The occurrence of SAEs and AESIs will also be monitored till 6 months after the study vaccination. The interim analysis is planned after all participants complete the Visit 5 at 28 days after the dosing, to evaluate the immunogenicity and safety within this period. The final analysis will be conducted after all participants complete the follow-up visit at 6 months post the booster vaccination, to evaluate the immunogenicity and safety.