Safety and Immunogenicity of Cell Culture-Derived A/H3N2 Variant Influenza Vaccines: A Phase I Randomized, Observer-Blind, Dose-Ranging Study

BACKGROUND: A/H3N2 variant (H3N2v) influenza may sustain human-to-human transmission, and an available candidate vaccine would be important. METHODS: In this phase I, randomized, observer-blind, dose-ranging study, 627 healthy subjects ≥ 3 years of age were randomized to receive 2 vaccinations with H3N2c cell-culture-derived vaccine doses containing 3.75 µg, 7.5 µg, or 15 µg hemagglutinin antigen of H3N2v with or without MF59 (registered trademark of Novartis AG) adjuvant (an oil-in-water emulsion). This paper reports Day 43 planned interim data. RESULTS: Single MF59-adjuvanted H3N2c doses elicited immune responses in almost all subjects regardless of antigen and adjuvant dose; the Center for Biologics Evaluation Research and Review (CBER) licensure criteria were met for all groups. Subjects with prevaccination hemagglutination inhibition titers <10 and children 3-<9 years achieve CBER criteria only after receiving 2 doses of nonadjuvanted H3N2c vaccine. Highest antibody titers were observed in the 7.5 µg + 0.25 mL MF59 groups in all age cohorts. MF59-adjuvanted H3N2c vaccines showed the highest rates of solicited local and systemic events, predominately mild or moderate. CONCLUSIONS: A single dose of H3N2c vaccine may be immunogenic and supports further development of MF59-adjuvanted H3N2c vaccines, especially for pediatric populations. CLINICAL TRIALS REGISTRATION: ClinicalTrials.gov identifier NCT01855945 (http://clinicaltrials.gov/ct2/show/NCT01855945).