Repeated dose toxicity and immunogenicity studies in SD rats: a new recombinant zoster vaccine (CHO cell) formulated with adjuvant BC02.

Herpes zoster, an infectious disease resulting from the reactivation of the varicella-zoster virus, is characterized by intense neuropathic pain. Safe and effective vaccination remains the optimal strategy for preventing and reducing associated complications. Recombinant zoster vaccine (CHO cell) (Qiuhong et al) employs a novel adjuvant system, BC02. This study aimed to conduct a comprehensive non-clinical safety assessment of RZV in adult Sprague-Dawley rats to support its entry into clinical trials. The rats received four (sp, one additional dose beyond the intended clinical three-dose schedule) doses of RZV. Safety was assessed using general health observations, immunotoxicity and immunogenicity assays, hematological and biochemical profiling, and histopathological evaluations. Aside from the changes observed in the adjuvant control group, no significant toxic effects were detected. No distinct target organs of toxicity were identified. The no-observed-adverse-effect level (NOAEL) was 1.0 mL per rat, which is equivalent to two human doses. The vaccine also elicited strong cellular and humoral responses, indicating its favorable immunogenicity. In summary, this systematic toxicology program supports the safety, tolerability, and immunogenicity of RZV and justifies its progression to human clinical trials.