Phase 1/2 clinical trial of COVID-19 vaccine in Japanese participants: A report of interim findings.

We initiated a randomized, placebo-controlled, phase 1/2 trial to evaluate the safety and immunogenicity of the S-268019-b recombinant protein vaccine, scheduled as 2 intramuscular injections given 21 days apart, in 60 randomized healthy Japanese adults. We evaluated 2 regimens of the S-910823 antigen (5 μg [n = 24] and 10 μg [n = 24]) with an oil-in-water emulsion formulation and compared against placebo (n = 12). Reactogenicity was mild in most participants. No serious adverse events were noted. For both regimens, vaccination resulted in robust IgG and neutralizing antibody production at days 36 and 50 and predominant T-helper 1-mediated immune reaction, as evident through antigen-specific polyfunctional CD4+ T-cell responses with IFN-γ, IL-2, and IL-4 production on spike protein peptides stimulation. Based on the interim analysis, the S-268019-b vaccine is safe, produces neutralizing antibodies titer comparable with that in convalescent serum from COVID-19-recovered patients. However, further evaluation of the vaccine in a large clinical trial is warranted.
Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: SI received payment or honoraria for lectures, presentations, speakers’ bureaus, manuscript writing, and educational events from Astellas Pharma Inc., Japan Vaccine Co., Ltd., Meiji Seika Pharma Co., Ltd., Pfizer Japan Inc., and Taisho Toyama Pharmaceutical Co. Ltd. TS, AK, RS, TH, SO, KI, and MA are employees of Shionogi & Co. Ltd..
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