Winterfield R W, Fadly A M, Hoerr F J
Avian Dis. 1976 Jan-Mar;20(1):42-8.
Study was made of the protection of chickens from spray vaccination with different modifications of a Holland (H) strain of infectious bronchitis virus (IBV). Noted in each trial were the virus-serum-neutralizing antibody titers induced and the virulence of the vaccine virus at different passage levels. Protection against respiratory signs was good from challenge with a homologous virus serotype as well as with 5 heterologous IBV isolates. This occurred from vaccinating day-old chicks possessing homologous IBV antibodies as well as vaccinating susceptible 4-week-old chickens. The tracheal virus shed-rate following challenge was considered low (20% or less) with 4 of the challenge viruses. The challenge virus shed-rate was somewhat higher from vaccination at one day old than from vaccination at 4 weeks; the virus-serum-neutralization titers were lower, or even insignificant, with early-age vaccination. The immunogenicity and virulence of the vaccine virus was apparently reduced in the higher embryo passages employed. None of the vaccine derivatives was considered virulent under these conditions.
对用传染性支气管炎病毒（IBV）荷兰（H）株的不同改良株进行喷雾免疫的雏鸡保护情况进行了研究。在每次试验中，都记录了诱导产生的病毒血清中和抗体效价以及不同传代水平下疫苗病毒的毒力。对于同源病毒血清型以及5种异源IBV分离株的攻击，对呼吸道症状的保护效果良好。这一情况出现在对具有同源IBV抗体的一日龄雏鸡进行免疫接种以及对易感的4周龄雏鸡进行免疫接种之后。对于4种攻击病毒，攻毒后气管病毒排出率被认为较低（20%或更低）。一日龄接种疫苗后的攻毒病毒排出率比4周龄接种疫苗后的略高；早期接种疫苗时，病毒血清中和效价较低，甚至不显著。在所采用的较高胚传代中，疫苗病毒的免疫原性和毒力明显降低。在这些条件下，没有一种疫苗衍生物被认为具有毒力。
