Efficacy and safety of a China-developed live attenuated herpes zoster vaccine in Chinese healthy adults aged 40 years and older: a multicentre, randomized, double-blind, placebo-controlled, phase 3 clinical trial.

Objectives: To evaluate the efficacy and safety of a live-attenuated gelatin-free herpes zoster (HZ) vaccine in adults ≥40 years.

Methods: In a multicentre, randomized, double-blind, placebo-controlled phase 3 trial (2020-2021, Zhejiang and Jiangsu provinces), HZ-naïve adults stratified by age (40-49, 50-59, 60-69, and ≥70 years) were randomized 1:1 to receive a single dose of the HZ vaccine (≥4.3 lg PFU) or placebo and followed for 13 months. The primary endpoint was the incidence of HZ; safety outcomes included adverse events (AEs) and serious AEs.

Results: The trial included 25 000 participants. HZ incidence was 5.3 versus 12.6/1000 person-years in the vaccine and placebo groups, respectively, resulting in a vaccine efficacy of 57.6% (95% CI: 43.1-68.7%) overall. Per age stratum, vaccine efficacy was 37.4% (95%CI: -117.0% to 83.9%), 62.7% (39.6-77.7%), 64.4% (42.5-78.7%), and 18.63% (-80.4% to 64.0%) in the 40-49, 50-59, 60-69, and ≥70 age groups, respectively. Few postherpetic neuralgia cases occurred (n = 13), limiting vaccine efficacy assessment. Solicited AEs were mild/moderate (13.8% [1719/12 491] vaccine vs. 5.1% [634/12 499] placebo), with no vaccine-related serious AEs. Grade 3 reactions, such as fever, were rare (0.06%, [7/12 491]), and AE rates declined with age (22.0% [219/995] in 40-49 vs. 9.1% [136/1499] in ≥70).

Discussion: China's gelatin-free HZ vaccine is safe and moderately effective, particularly in adults aged 50-69 years, with an age-dependent safety profile.