Phase II, Safety and Immunogenicity of RAZI Cov Pars (RCP) SARS Cov-2 Vaccine in Adults Aged 18–70 Years; A Randomized, Double-Blind Clinical Trial

Background This study explores the safety and immunogenicity of the Razi-Cov-Pars (RCP) SARS Cov-2 recombinant spike protein vaccine. Method In a randomized, double-blind, placebo-controlled trial, adults aged 18-70 were randomly allocated to receive selected 10µg/200µl vaccine strengths or placebo (adjuvant). It included two intramuscular injections at days 0 and 21, followed by an intranasal dose at day 51. Immediate and delayed solicited local and systemic adverse reactions after each dose up to a week, and specific IgG antibodies against SARS Cov-2 spike antigens two weeks after the 2nd dose were assessed as primary outcomes. Secondary safety outcomes were abnormal laboratory findings and medically attended adverse events (MAAE) over six months follow up. Secondary immunogenicity outcomes were neutralizing antibody activity and cell-mediated immune response. Result Between May 27th and July 15th, 2021, 500 participants were enrolled. Participants' mean (SD) age was 37.8 (9.0), and 67.0 % were male. No immediate adverse reaction was observed following the intervention. All solicited local and systemic adverse events were moderate (Grade I-II). Specific IgG antibody response against S antigen in the vaccine group was 5.28 times (95%CI: 4.02-6.94) the placebo group with a 75% seroconversion rate. During six months of follow-up, 8 SAEs were reported, unrelated to the study intervention. The participants sustained their acquired humoral responses at the end of the sixth month. The vaccine predominantly resulted in T-helper 1 cell-mediated immunity, CD8+ cytotoxic T-cell increase, and no increase in inflammatory IL-6 cytokine. Conclusion RCP vaccine is safe and creates strong and durable humoral and cellular immunity. Trial registration (IRCT20201214049709N2).