Effectiveness and safety of a novel intranasal influenza vaccine in Chinese children: A phase IV multi-Center, randomized, double-blind, placebo-controlled clinical trial

Abstract

BACKGROUND: A novel intranasal influenza vaccine named Ganwu® was approved in 2020 for children aged 3-17 years in China. This study aimed to conduct a phase IV clinical trial to assess the effectiveness and safety of this vaccine. METHODS: We conducted a multicenter, randomized, double-blind, placebo-controlled phase IV clinical trial to evaluate the effectiveness and safety of Ganwu® vaccine in children aged 3-17 years in China during 2023 to 2024 influenza season. The influenza-like illnesses (ILIs) were monitored in the vaccine and placebo groups during a follow-up period of seven months, and nasopharyngeal specimens from ILI cases were collected for laboratory confirmation of influenza virus. Primary endpoints included vaccine effectiveness against laboratory-confirmed influenza and ILI, with comprehensive safety monitoring throughout the study period. RESULTS: The trial enrolled 6000 participants, randomly allocated in a 1:1 ratio to receive either Ganwu® or placebo. The vaccine's effectiveness in preventing laboratory-confirmed influenza was 46.8 % (95 % confidence interval [CI] 25.8 %-61.9 %), with specific effectiveness rates of 30.4 % against A/H1N1, 55.1 % against A/H3N2, and 84.6 % against B/Victoria. Laboratory-confirmed influenza was significantly less frequent in the vaccine group (hazard ratio 0.53, 95 % CI 0.38-0.74). Effectiveness of Ganwu® vaccine against ILI was 15.2 % (95 % CI -2.3 %-29.7 %). Safety assessments demonstrated comparable incidence of solicited adverse events (AE) between groups, with the incidence of grade three or higher AEs below 1 %. Among 12 reported serious AEs, none were attributed to vaccination. CONCLUSIONS: Ganwu® vaccine provided moderate protection against laboratory-confirmed influenza among children with good safety profile.