Low pathogenic avian influenza virus is one of the major threats that has been affecting the poultry industry in the Middle East region for decades. Attempts to eradicate this disease have failed. Currently, there are commercial vaccines that are either imported or produced locally from recently circulating isolates of H9N2 in Egypt and Middle Eastern countries. This present work focused on comparing the effectiveness of two vaccines belonging to these categories in Egypt. Two commercial broiler flocks (Cobb-500 Broiler) with maternally derived immunity (MDA) against H9N2 virus were employed and placed under normal commercial field conditions or laboratory conditions. Immunity was evaluated on the basis of detectable humoral antibodies against influenza H9N2 virus, and challenge was conducted at 28 days of life using a recent wild H9N2 virus. The results showed that vaccination on the 7th day of life provided significantly higher immune response in both vaccine types, with significantly lower virus shedding compared to vaccination at day 1 of life, regardless of field or laboratory conditions. In addition, the vaccine produced from a recent local H9N2 isolate (MEFLUVAC-H9-16) provided a significantly higher humoral immune response under both field and laboratory conditions, as measured by serology and virus shedding (number of shedders and amount of shedding virus), being significantly lower following challenge on the 28th day of life, contrary to the imported H9 vaccine. In conclusion, use of H9N2 vaccine at 7 days of life provided a significantly higher protection than vaccination at day 1 of life in birds with MDA, suggesting vaccination regimes between 5–8-days of life for broiler chicks with MDA. Moreover, use of a vaccine prepared from a recently circulating H9N2 virus showed significantly higher protection and was more suitable for birds in the Middle East.

中文翻译：

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两种不同疫苗接种方案对肉鸡H9N2禽流感的有效性比较

低致病性禽流感病毒是数十年来一直影响中东地区家禽业的主要威胁之一。根除这种疾病的尝试失败了。当前，有商业疫苗是从埃及和中东国家最近流行的H9N2分离株中本地进口或生产的。这项当前的工作集中在埃及比较属于这两个类别的两种疫苗的有效性。使用两个具有母源衍生的针对H9N2病毒的免疫（MDA）的商业肉鸡群（Cobb-500肉鸡），并将其置于正常的商业现场条件或实验室条件下。在针对H9N2流感病毒的可检测体液抗体的基础上评估了免疫力，并使用最近的野生H9N2病毒在生命的28天进行了攻击。结果表明，与生命的第1天接种相比，两种疫苗类型在生命的第7天进行疫苗接种均显着提高了免疫反应，而病毒的释放则显着降低，无论现场或实验室条件如何。此外，从最近的局部H9N2分离株（MEFLUVAC-H9-16）生产的疫苗在野外和实验室条件下均提供了更高的体液免疫反应，这可以通过血清学和病毒脱落（脱落数量和脱落病毒数量）来衡量与进口的H9疫苗相反，在出生后第28天接受挑战后的抵抗力明显降低。总之，对于MDA禽类，在生命7天使用H9N2疫苗比在生命第一天接种疫苗提供了更高的保护，建议患有MDA的肉仔鸡在5至8天的生命中进行疫苗接种。此外，使用由最近传播的H9N2病毒制备的疫苗显示出更高的防护性，并且更适合中东地区的鸟类。