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 g , 7.5 g , or 15 g hemagglutinin antigen of H3N2v with or without MF59 ( registered trademark of Novartis AG ) adjuvant ( an oil-in-water emulsion ) .