Seasonal Influenza Vaccine Effectiveness in a Tropical Developing African Country

描述（由研究者提供）：流感是几乎每年发病和死亡的主要原因；当流行病发生时，其影响更为严重。大流行病毒可能是人类病毒与携带禽流感基因的动物流感病毒重新组合的结果。这种重新组合可能更容易发生在热带气候中，在那里人类和动物病毒全年经常共同传播。很少有数据记录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难以制定针对季节性流感或大流行性流感的流感控制战略。有效的灭活流感疫苗已经有几十年的历史了，但是缺乏数据来说明它们在保护热带发展中国家的接种者方面的有效性，以及它们在这些人群中减少传播的能力。来自发达国家的一些报告表明，如果将流感疫苗接种给少数对传播负有最大责任的人（通常是儿童），就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，在发展中国家环境中可能可行的有针对性的使用可能会减少社区中的流感感染。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采取干预措施，以遏制或减弱大流行的影响。因此，为了评估三价灭活流感疫苗在热带发展中国家的有效性，我们建议在塞内加尔进行一项观察者盲、集群随机、主动对照、平行组的IV期试验。该试验将进行三年，目标是6个月至10岁的儿童接种疫苗。不仅将估计儿童疫苗接种者的有效性，而且还将衡量社区其他部分的间接有效性。在整个研究过程中，将进行哨点监测和主动监测，以记录参与者和社区中流感样疾病的发生情况。主要结果将是预防符合病例定义的有症状的实验室确诊流感。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群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 investigator): 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 viruses with animal influenza viruses carrying avian influenza genes. 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. 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, active-control, parallel-group, phase IV trial 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 influenza-like 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.