Safety and immunogenicity of COReNAPCIN(R), a SARS-CoV-2 mRNA vaccine; a randomized, double-blind, placebo-controlled phase 1 clinical trial

The repeated COVID-19 outbreaks, despite global vaccination, highlights the need for booster doses. Here, we present the outcomes, up until day 90 post vaccination, of a randomized, double-blind, placebo-controlled phase 1 clinical trial of the mRNA-based vaccine candidate; COReNAPCIN(R), as a booster dose in adults aged 18-50 who had previously received three doses of inactivated vaccines. In the study, 30 participants randomly (2:2:1) received 25 g, or 50 g of COReNAPCIN(R), or placebo. The results indicated that COReNAPCIN(R) was well tolerated in vaccinated individuals in both groups with no life-threatening or other serious adverse events. The most noticeable solicited adverse events were pain at the site of injection, fatigue and myalgia. Regarding the immunogenicity, given the seroprevalence of SARS-CoV-2 antibodies due to the vaccination history for all, and previous SARS-CoV-2 infection for some participants, the recipients of COReNAPCIN(R), two weeks post vaccination, showed significant fold increases in the level of anti-RBD (6.6 and 8.1 folds) or anti-spike (11.5 and 21.7 folds), and potent neutralizing antibodies (10.2 and 8.4 folds) in 25 and 50 g groups, respectively, while no meaningful changes were observed in the placebo group. Additionally, the significant increase in the spike-specific IFN-{gamma} T-cell response upon vaccination, underscores the activation of cellular immunity. Altogether, the favorable safety, tolerability, and immunogenicity profile of COReNAPCIN(R) support its further clinical development. Trial registration numberIRCT20230131057293N1