Al-Garib et
al. (2003) also reported that after vaccination with
inactivated vaccine, HI response was recorded at 14
DPV. In serum, IgM was firstly detected at 14 DPV
and remained at a high level until 28 DPV. IgG and a
low IgA response were detected from 14 DPV
onward. In trachea, IgM and IgG responses were
detected from 7 and 14 DPV, respectively, but IgA
response was not observed. Based on this fact, the
early protection after vaccination was mainly due to
immunization with live attenuated vaccine and the
protection at 14 DPV was the result of immunity
induced by both type of vaccines.