To stimulate active immunity against very virulent infectious bursal disease viruses in broiler chickens from hens vaccinated against IBD. The vaccine contains the live intermediate plus IBDV strain Winterfield 2512 bound to specific immunoglobulins. Both components form a complex which is administered through vaccination. The Winterfield 2512 vaccine virus, applied as a non-immune-complex vaccine results in a mean histological lesion score of 2.2 in the bursa of Fabricius, 28 days after vaccination (after oral vaccination of 1-day-old SPF chicken with 10 doses). The severity and duration of lesions is less significant following administration of the immune-complex vaccine.