Seasonal Influenza Vaccine Effectiveness in a Tropical Developing African Country

描述(申请人提供)：流感几乎每年都是发病率和死亡率的主要原因；当大流行发生时，影响更严重。大流行病毒可能是人类流感病毒与动物流感病毒重新分类的结果。在人和动物病毒全年频繁共同传播的热带气候中，这种重新分类可能更容易发生。几乎没有数据可以证明流感在热带发展中国家的传播和负担。在这种情况下，如果不能更好地了解流感流行病学，国家和全球公共卫生官员就很难制定季节性或大流行性流感的流感控制战略。有效的灭活流感疫苗几十年来一直存在，但缺乏关于它们对保护热带发展中国家接受者的有效性以及它们减少这些人群传播的能力的数据。发达国家的一些报告表明，当流感疫苗接种给数量有限、对传播负有最大责任的人，通常是儿童时，有可能阻断传播并减轻社区的总体流感负担。流感疫苗为未接种疫苗的个人提供间接保护的潜力表明，有针对性的使用可能在发展中国家环境中是可行的，可能会减少社区中的流感感染，而不是接种疫苗的人。在大流行的情况下，这些努力可以减缓大流行病毒的传播，并为公共卫生官员提供足够的时间来引入干预措施，以遏制或削弱大流行的影响。因此，为了评估三价灭活流感疫苗在一个热带发展中国家的有效性，我们建议在塞内加尔进行一项新的佐剂流感疫苗的观察者盲法、整群随机、对照、平行组试验。这项试验将在三年内进行，目标是6个月至10岁的儿童接种疫苗。不仅将评估儿童疫苗接受者的有效性，还将衡量社区其余部分的间接有效性。在整个研究过程中，将进行定点和积极监测，以记录参与者和社区发生发热性急性呼吸道疾病的情况。主要成果将是预防实验室确认的符合病例定义的症状性流感。监测还将使我们能够通过确定实验室确认的流感发病率和描述人口中流感的临床特征来描述热带发展中国家的流感流行病学。

DESCRIPTION (provided by applicant): Influenza is a major cause of morbidity and mortality nearly every year; when pandemics occur, the impact is even more severe. A pandemic virus may result from reassortment of human influenza viruses with animal influenza viruses. Such reassortment may occur more readily in tropical climates where human and animal viruses frequently co-circulate throughout the year. Few data are available to document the transmission and burden of influenza in tropical developing countries. Without a better understanding of influenza epidemiology in such situations, it is difficult for national and global public health officials to develop influenza-control strategies for either seasonal or pandemic influenza. Effective inactivated influenza vaccines have been available for decades, but data are lacking on their effectiveness for both protecting recipients in tropical developing countries and also their ability to reduce transmission in such populations. A number of reports from developed countries indicate that influenza vaccine, when given to a limited number of persons most responsible for transmission, usually children, has the potential to interrupt transmission and reduce the overall influenza burden in a community. The potential of influenza vaccine to provide indirect protection to unvaccinated individuals suggests that targeted use, which may be feasible in developing-country settings, might reduce influenza infection in the community beyond those who were vaccinated. In a pandemic situation, these efforts could slow the spread of pandemic virus and provide sufficient time for public health officials to introduce interventions to contain or blunt the effects of a pandemic. Thus, to evaluate the effectiveness of trivalent, inactivated influenza vaccine in a tropical developing country, we propose to conduct an observer- blind, cluster-randomized, controlled, parallel-group trial of a new adjuvanted influenza vaccine in Senegal. The trial will take place over a three-year period and will target children 6 months to 10 years of age for vaccination. Not only will effectiveness be estimated for child vaccine recipients, but indirect effectiveness will also be measured for the rest of the community. Throughout the course of the study, both sentinel and active surveillance will be conducted to document the occurrence of febrile acute respiratory illness among participants and in the community. The primary outcome will be prevention of symptomatic laboratory- confirmed influenza meeting a case definition. Surveillance will also allow us to describe the epidemiology of influenza in a tropical developing country by defining the rates of laboratory-confirmed influenza and by describing the clinical characteristics of influenza in the population.