Pirbright Laboratory, Institute for Animal Health, Ash Road, Pirbright, Woking, Surrey GU24 0NF, UK.
Vaccine. 2010 Mar 8;28(11):2318-22. doi: 10.1016/j.vaccine.2009.12.065. Epub 2010 Jan 5.
To determine the longevity of protective immunity following a single administration of emergency vaccine, and establish whether the immune response could be enhanced by increasing the antigen payload even further, cattle were vaccinated with an A22 Iraq vaccine containing either 1x antigen payload (field dose) or 5x antigen payload. Six months post-immunisation all cattle received a homologous virus challenge. The magnitude of the virus neutralising antibody response elicited was consistent with the response to similarly formulated A serotype vaccines with a PD(50) greater than 32. All the vaccinated cattle, regardless of antigen payload, were protected from clinical disease following challenge although some cattle in both groups became sub-clinically infected. We conclude that immunisation with a single inoculation of vaccine from the UK emergency reserve can protect cattle from clinical disease for at least 6 months post-vaccination and that a boost may be unnecessary in an outbreak situation. Some animals may become sub-clinically infected but this is likely to be dependent on the severity of challenge. The study confirmed that a booster at 21 days post-vaccination was not necessary to maintain a cell-mediated response in cattle for 6 months. No increased benefits were recognised by increasing the antigen payload of this vaccine 5x.
为了确定单次紧急疫苗接种后保护性免疫的持久性，并确定是否可以通过进一步增加抗原载量来增强免疫反应，将含有 1x 抗原载量（田间剂量）或 5x 抗原载量的 A22 伊拉克疫苗接种给牛。免疫后 6 个月，所有牛都接受了同源病毒挑战。病毒中和抗体反应的幅度与类似配方的 A 血清型疫苗的反应一致，PD（50）大于 32。所有接种疫苗的牛，无论抗原载量如何，在接种后都能免受临床疾病的侵害，尽管两组中的一些牛都出现了亚临床感染。我们得出结论，使用来自英国应急储备的单次接种疫苗可以保护牛免受临床疾病至少 6 个月，并且在爆发情况下可能不需要加强免疫。一些动物可能会出现亚临床感染，但这可能取决于挑战的严重程度。该研究证实，在接种疫苗后 21 天加强免疫对牛的细胞介导反应维持 6 个月是不必要的。增加这种疫苗的抗原载量 5 倍并没有带来额外的益处。
