Duration of immunity produced by a live attenuated vaccine against avian pneumovirus type C.

A recently developed live, attenuated vaccine against avian pneumovirus (APV) was found to be safe and protective in experimental birds. Duration of immunity following a single dose of this experimental vaccine in 1-week-old turkey poults is described. Two groups each of 60 poults were housed in separate isolation rooms. Birds in group one were inoculated oculonasally at 1 week of age with the vaccine. The second group served as a non-vaccinated group and was inoculated with mock-infected cell culture fluid. At 3, 7, 10, and 14 weeks post vaccination, 15 birds from each of the groups were removed to separate isolation rooms and challenged with virulent APV. Taken together, data on clinical signs and virus detection in choanal swabs following each challenge indicated that the vaccine was able to protect birds for up to 14 weeks post vaccination. Peak antibody levels were attained 7 weeks post vaccination and declined thereafter. These results indicated that this experimental vaccine induced protection against APV even in the absence of high antibody titres.