Estimating vaccine efficacy in prospective studies

Vaccine efficacy may be estimated by comparing affected proportions or incidence rates between groups of vaccinates and non-vaccinates. This paper discusses vaccine efficacy assessment and reviews interval estimation methods for summary measures from clinical trials and cohort studies of a protective exposure. The measures considered are the attributable fraction as the complement of the risk ratio or incidence density ratio, and the difference in risks or incidence densities. A simple formula is developed for the score method of estimating the incidence density ratio. The application of these methods is illustrated using recent reports of veterinary vaccine studies.     

优化抗球虫病疫苗在肉鸡的效力

抗球虫病疫苗的成功应用,不仅仅是简单地将疫苗用于雏鸡就了事。为了获得保护性免疫力从而产生最佳的经济效益,必须对免疫接种的方法加以精心控制,必须对卵囊的摄入量和产生的免疫力进行监测,开发出的防制措施还必须能够确保生长中肉鸡的一般健康和福利需求以及肉鸡所处环境的质量。     

影响禽用疫苗效果的因素

影响疫苗效果的因素可以分为三个主要部分，一是疫苗的质量；二是使用方法：三是家禽自身的原因。我们在分析疫苗效果的时候，应尽可能考虑养殖场所有可能存在的实际影响因素，同时也应注意到由于不正确的诊断方法而导致的对疫苗效果的否定。     

A live Pasteurella haemolytica vaccine efficacy trial

A live Pasteurella haemolytica serotype 1 vaccine was used in an efficacy trial conducted on 100 lightweight feeder calves purchased from a Florida ranch. Forty-one calves were inoculated with the vaccine intradermally in the neck. Fifty-nine calves served as nonvaccinated controls. Fourteen days later, the calves were shipped to an order buyer in eastern Tennessee, where the calves were mixed with 60 local calves in a community sale barn for 72 hours. After 3 additional days, the calves were shipped to a research feedlot in Bushland, Tex. They remained in the feedlot for 56 days, and the test was concluded 76 days after vaccination. The P haemolytica vaccine had no significant effect on performance, morbidity, or mortality. There was no significant difference between the vaccinated and nonvaccinated calves in the number of times Pasteurella was isolated. The calves became seropositive to bovine viral diarrhea virus, respiratory syncytial virus, and infectious bovine rhinotracheitis (IBR) virus during the 76-day experiment. All calves initially were seropositive to parainfluenza-3 virus. A virulent outbreak of IBR occurred 30 days after the calves arrived at the feedlot. Before the onset of IBR, the isolation of P haemolytica serotype 1 from nasal turbinates was rare (2 of 500 nasal swabs). After the IBR outbreak, P haemolytica serotype 1 was isolated from 40 of 92 calves.     

鸡球虫微囊型疫苗的研制及免疫效果

研制了微囊型鸡球虫疫苗并对其免疫效果进行探讨。结果表明,强毒微囊组获得的饲养效果最好,其相对增重率和相对饲料转换率分别为104.8%和100%;弱毒水剂组为74.1%和136%,而弱毒微囊组为49.4%和188%。强毒微囊组对球虫病的控制效果也明显好于其他组,其发病率、病变记分、血便记分分别为20%,6分和3分,而弱毒水剂组和弱毒微囊组分别为40%、10分、7分和50%、18分、8分。所研制的这种新型微囊球虫疫苗,具有使用方便,节省人力物力;疫苗大小适中,流动性好容易与小鸡饲料混合均匀等优点。由于微囊型球虫疫苗投服方便,因此能适合各种规模的鸡场使用,也适合鸡场进行多次或长期免疫使用。这种微囊剂型球虫疫苗的进一步完善和推广应用,可为我国鸡球虫病的免疫预防提供新的剂型。     

提高DNA疫苗免疫效力的策略

DNA疫苗以其独特优点而倍受青睐，但免疫效力较低制约着其广泛应用。本文从佐刺的使用、优化表达载体．优化抗原基因等方面综述了提高DNA疫苗免疫效力的策略，并对DNA疫苗前景进行了展望。     

山羊痘活疫苗临床免疫效果观察

1材料与方法 1.1主要试剂和器材山羊痘琼扩抗原和阳性血清、山羊痘野生强毒、山羊痘参考阳性抗原,兔抗山羊痘高免血清,山羊痘标准阴性血清,其他常见动物病血清以及山羊痘反向间接血凝诊断液由贵州大学动物医学院提供,山羊痘抗体检测也在贵州大学动物医学院进行.     

禽用DNA疫苗免疫效果增强的策略

对于人和动物的传染病来说,DNA疫苗免疫是一种很有希望的免疫方式。经过25年的发展,已经上市的核酸疫苗仍屈指可数。禽用核酸疫苗一直是禽类疫苗的研究热点,文中描述提高核酸疫苗免疫效果的方式：接种途径,疫苗剂量及首免时间,增加宿主细胞对质粒的摄入,添加免疫增强分子,优化质粒骨架和密码子,疫苗抗原的选择,异源性的首免-加强免疫策略。     

New technology for improved vaccine safety and efficacy.

Nearly all of the 2000 vaccines presently licensed by the US Department of Agriculture for veterinary use in the United States are conventional vaccines containing either killed or modified live whole bacteria or viruses. Recent advances in molecular biology, immunology, microbiology, and genetics and in understanding microbial pathogenesis have led to the development of a wide variety of new approaches for developing safer and more effective vaccines. This article briefly describes these new technologies and their potential advantages and disadvantages as compared with conventional killed and modified live vaccines.     

Epididymitis in rams: studies on vaccine efficacy.

Simultaneous inoculation with Br. ovis bacterin plus Br. abortus strain 19 produced the greatest immunity. This procedure was not permitted, however, as widespread use of Br. abortus in sheep might pose a hazard to the brucellosis eradication program in cattle. Subsequent work demonstrated that an aluminum hydroxide adsorbed bacterin, administered as two injections spaced 3-6 weeks apart, conferred a significant and acceptable level of immunity.     

牛冠状病毒灭活疫苗的免疫效力试验

为了评价制备的牛冠状病毒灭活疫苗的免疫效力,试验选用分离鉴定出来的牛冠状病毒(BCV-YC分离株)为制苗种毒,接种HRT-18细胞进行增殖,收集上清液进行超速离心浓缩,最后加入甲醛灭活制成油乳剂灭活疫苗,分别接种小鼠和妊娠母牛。结果表明,疫苗不仅使小鼠具有一定的保护力,而且使妊娠母牛也能产生较高的抗体水平,犊牛攻毒试验证明,产生的母源抗体能使初生犊牛抵抗牛冠状病毒的攻击。说明制备的牛冠状病毒灭活疫苗对抵抗牛冠状病毒感染具有良好的保护性。     

四价鸡球虫苗的免疫效果研究

在实验条件下观察自主研制的四价鸡球虫苗(LCV)对平养鸡的安全性和免疫保护效果.试验设空白对照组(NC)、攻虫对ECX(PC)和免疫组(VC)3个试验组,每组30只鸡.试验结果:空白对照组、攻虫对照组和免疫组的相对增重率依次为100%、84.77%和94.97%;免疫后(免疫后攻虫前)排卵囊高峰期间(免疫后5 d～10 d),免疫组平均OPG(即每克粪便申的卵囊数)为2.70 X 104,攻虫后排卵囊高峰期间(攻虫后6 d～13 d)攻虫对照组组平均OPG为2.32 X 106,高于免疫组(2.69 X 103)(P<0.01);攻虫后各组死亡率依次为0、10%和o;3个组的ACI(抗球虫指数)分别为200,0、154.77和184.97,免疫组试验效果最佳.结果表明,LCV安全性高、免疫保护效果理想.接种该疫苗后的鸡对较大剂量攻虫具有较强的抵抗力.     

猪圆环病毒2型灭活疫苗效力检验中参考疫苗的应用

制备了4批不同抗原含量的猪圆环病毒2型（PCV2）灭活疫苗,灭活前PCV2病毒含量分别为107.0、106.5、105.5和104.5TCID50/mL。对此4批PCV2灭活疫苗,利用本实验室建立的小白鼠效力检验标准进行效力检验,即以PCV2参考疫苗作为对照品,测定待检疫苗免疫小白鼠后血清中PCV2抗体效价的高低来判定疫苗效力。3次重复检测结果都显示灭活前病毒含量为107.0、106.5和105.5TCID50/mL批次的疫苗合格,而灭活前病毒含量为104.5TCID50/mL批次的疫苗不合格,这与猪体内的效力检验结果一致,表明建立的针对猪圆环病毒2型灭活疫苗的小白鼠效力检验方法具有良好的准确性和重复性。     

Influence of a reovirus-antibody complex vaccine on efficacy of Marek's disease vaccine administered in ovo

Two experiments determined the influence of an experimental reovirus-antibody complex vaccine on Mareks disease virus (MDV) vaccine when used in ovo. Designs were the same except that specific-pathogen-free (SPF) broiler eggs were used in Experiment 1 and commercial broiler eggs with maternal antibodies against reovirus were used in Experiment 2. At 18 days of incubation, embryos were separated into four groups and inoculated with either diluent, MDV vaccine, reovirus-antibody complex vaccine, or a combination of reovirus-antibody complex and MDV vaccine. At 5 days of age, half the chickens in each group were challenged with MDV. At 7 wk old, all were euthanatized, weighed, and examined. At 7 days of age, remaining chickens in each group were challenged with reovirus. At 21 days old, chickens were euthanatized and weighed. No vaccine adversely affected hatchability or posthatch mortality in SPF or commercial chickens. There were no significant differences in protection against reovirus challenge when vaccines were used separately or in combination, and lesion scores were nearly identical in all vaccinated groups in both experiments. However, percentage of protection against reovirus was lower in Experiment 2, indicating an adverse effect of maternal immunity on efficacy of the reovirus vaccine. There were no significant differences in protection against MDV when the vaccines were used separately or combined. Severity of MDV lesions was nearly identical in all vaccinated groups in both experiments. However, the combination of vaccines gave numerically lower protection against MDV than MDV vaccine alone. Use of a larger number of birds, as in field conditions, may result in statistically lower protection for the vaccine combination. Large field trials are needed to determine the potential of the reovirus-antibody complex vaccine.     

The efficacy of a Giardia lamblia vaccine in kittens.

Twenty kittens were vaccinated with a Giardia lamblia vaccine prepared on a commercial scale on day 0 and boosted on day 21 (group 1); while 10 kittens received only saline (group 2). These kittens were challenged on day 35 with 10(6) Giardia lamblia trophozoites by a surgical intraduodenal injection. Three control kittens were not vaccinated and not challenged (group 3). Following challenge, Giardia vaccinated kittens had significantly fewer days in which abnormal stools were observed and reduced food intake occurred compared to saline injected animals. The rate of weight gain between group 1 and group 2 animals was not different in the prechallenge period (day 0 to day 35), but vaccinated animals had a significantly higher weight gain in the postchallenge period (P < 0.05). On day 56, all vaccinated animals were not passing cysts in their feces, while 40% of saline injected kittens had Giardia cysts in their feces. In vaccinated kittens, cysts were never demonstrated in 45% of the animals, while cysts were detected in 90% of the saline injected kittens. Viability of the cysts in vaccinated kittens was 38% while the cysts viability in saline injected kittens was 99%. On postmortem examination, trophozoites could be detected in 5% of vaccinated kittens and 60% of saline injected kittens. Vaccination produced an elevated Giardia specific serum IgG and IgA response prior to challenge and throughout the postinfection period. The Giardia infection in the saline injected group did not induce an elevated specific serum response. Giardia vaccination of kittens provides protection in kittens from an experimental challenge by reducing or eliminating intestinal trophozoites and fecal cyst excretion.