Abstract

The varicella vaccine (VarV) produced by Sinovac (Dalian) obtained World Health Organization (WHO) prequalification in November 2022. However, no direct comparative studies have been conducted between VarV and other WHO-prequalified varicella vaccines. The study aimed to assess the immunogenicity and safety of Sinovac’s VarV compared with Merck Sharp & Dohme’s (MSD) VARIVAX® following a single dose administration. This Phase III, randomized, double-blind, active-controlled, non-inferiority trial conducted in the Philippines. Healthy children aged 12 to 15 months were enrolled. Eligible participants were randomly assigned (1:1) to receive a single dose of varicella vaccine either manufactured by Sinovac (Test group) or MSD (Active control group).Immunogenicity was evaluated 6 weeks after vaccination by enzyme-linked immunosorbent assay. The primary immunogenicity endpoint was seroresponse rate in participants who were seronegative at baseline (varicella-zoster virus antibodyconcentration ＜ 10 mIU/mL), as well as the secondary endpoint geometric meanconcentration (GMC). Adverse events (AEs) were monitored for 6 weeks after vaccination. Among 484 participants analyzed, seroresponse rates were 98.85% and 98.88% in the Test group and Active control group, respectively, with a difference of -0.03% (95% CI: – 3.10%, 2.99%). GMCs were 35.73 mIU/mL and 37.34 mIU/mL, respectively, with the ratioof 0.96 (95% CI: 0.86, 1.06). Both immunogenicity endpoints reached the prespecified non-inferiority criteria. Furthermore, the incidence of adverse reactions (ARs) in the Test group was lower than that in the Active control group (38.08% vs 55.51%). Conclusions: Sinovac’s VarV demonstrated non-inferior immunogenicity to WHO-prequalified comparator vaccine (VARIVAX®) and favorable safety profile. These findings indicated that VarV (Sinovac) met WHO standards for varicella vaccine evaluation, supporting its global use consideration.