A method of producing active immunity against a viral disease in an animal subject comprises administering to the subject a vaccine conjugate consisting essentially of a live virus and a neutralizing factor bound to the live virus. The neutralizing factor is selected from the group consisting of antibodies and antibody fragments. The live virus is one capable of producing disease in the subject, and the antibody or antibody fragment is one capable of neutralizing the live virus. Preferred subjects are birds, a preferred virus is Infectious Bursal Disease Virus, and a preferred route of administration to birds is by in ovo administration.