Open-label, randomised, parallel-group, multicentre study to evaluate the safety, tolerability and immunogenicity of an AS03(B)/oil-in-water emulsion-adjuvanted (AS03(B)) split-virion versus non-adjuvanted whole-virion H1N1 influenza vaccine in UK children 6 months to 12 years of age.

Background: Children are a priority for vaccination in an influenza pandemic, but safety and immunogenicity data for new-generation adjuvanted and whole-virion vaccines are limited. Objectives: Immunogenicity •How does the percentage of children aged 6 months to 12 years of age with a fourfold rise in microneutralisation titres between the prevaccination sample and the sample taken 3 weeks after completion of a two-dose course of the non-adjuvanted, whole-virion vaccine and the AS03B-adjuvanted split-virion vaccine compare? •How does the percentage of children aged 6 months to 12 years of age with haemagglutination inhibition titres of ? 1 : 32 3 weeks after completion of a two-dose course of the non-adjuvanted, whole-virion vaccine and the AS03B-adjuvanted split-virion vaccine compare? •How does the percentage of children aged 6 months to 12 years of age with a fourfold rise in haemagglutination inhibition titres between the prevaccination sample and the sample taken 3 weeks after completion of a two-dose course of the non-adjuvanted, whole-virion vaccine and the AS03B-adjuvanted split-virion vaccine compare? •What is the geometric mean fold rise in haemagglutination inhibition titres from baseline to 3 weeks after two doses of the non-adjuvanted, whole-virion vaccine and the AS03B-adjuvanted split-virion vaccine? •What is the geometric mean haemagglutination inhibition titre 3 weeks after two doses of the non-adjuvanted, whole-virion vaccine and the AS03B-adjuvanted split-virion vaccine? Reactogenicity •How does the percentage of children aged 6 months to 12 years of age experiencing fever and local reactions within the 7 days following each dose of the non-adjuvanted, whole-virion and the AS03B-adjuvanted split-virion vaccines compare? •What percentage of children aged 6 months to 12 years of age experience non-febrile systemic reactions within the 7 days following each dose of the non-adjuvanted, whole-virion and the AS03B-adjuvanted split-virion vaccine? Methods: The safety, reactogenicity and immunogenicity of a tocopherol/oil-in-water emulsion-adjuvanted (AS03B) egg culture-derived split-virion H1N1 vaccine and a non-adjuvanted cell culture-derived whole-virion vaccine, given as a two-dose schedule, 21 days apart, were compared in a randomised, open-label trial of children aged 6 months to 12 years of age. Local reactions and systemic symptoms were collected for 1 week post immunisation, and serum was collected at baseline and after the second dose. Results: Among 937 children receiving vaccine, per-protocol seroconversion rates were higher after the AS03B-adjuvanted vaccine than after the whole-virion vaccine (98.2% vs 80.1% in children 38.0°C in those under 5 years of age (8.9% vs 22.4%). Conclusion: In this first direct comparison of an AS03B-adjuvanted split-virion vaccine versus whole-virion non-adjuvanted H1N1 vaccine, the adjuvanted vaccine – while reactogenic – was more immunogenic, especially in younger children, indicating the potential for improved immunogenicity of influenza vaccines in this age group.