Newcastle Disease-Infectious Bronchitis Inactivated Combined Vaccine

Abstract

Immunogenicity and safety of Newcastle disease (ND) infectious bronchitis (IB) inactivated combined vaccine (the combined vaccine for short) were studied in chickens 4 to 40 days old. ND hemagglutinationinhibition (HI) titer was 16 to 50 in a group of birds inoculated with the combined vaccine. It was 32 to 56 in a group of birds inoculated with ND vaccine Namely, there was no difference in titer between the two groups.
IB neutralization (NT) titers were 3.0 to 4.0 in a group inoculated with the combined vaccine and a group inoculated with IB vaccine. There was no difference in titer between the two groups.
In the groups inoculated with the combined vaccine, ND HI titer reached a maximum approximately 4 weeks postvaccination and then dropped, but IB NT titer maintained a high level until 8 weeks postvaccination.
A rise in ND HI titer and IB NT titer was insufficient in birds 4 to 10 days old because of the presence of maternal antibodies.
In these trials, no death or any noticeable clinical symptom occurred to the birds inoculated with the combined vaccine. Both ND HI titer and IB NT titer showed a satisfactory rise.