title: An outbreak of typhoid fever, Xing-An County, People's Republic of China, 1999: estimation of the field effectiveness of Vi polysaccharide typhoid vaccine.
abstract: To evaluate the effectiveness of Vi polysaccharide vaccine (Vi vaccine) in preventing typhoid fever, an analysis was done of an outbreak of typhoid fever among students attending a middle school in the People's Republic of China, where Vi vaccine is licensed for use. Vi vaccine effectiveness was analyzed by using Cox proportional hazards modeling to account for the time-dependent nature of vaccination and illness status during the outbreak. Among 1260 students who had been immunized before the outbreak, receipt of Vi vaccine was associated with 73% (95% confidence interval [CI], 32%-89%) protection. Among the additional 441 students immunized during the outbreak, receipt of Vi vaccine was associated with 71% (95% CI, -9% to 92%) protection. These results provide the first evidence about the effectiveness of Vi vaccine when deployed routinely in a typhoid-endemic area and support the use of Vi vaccine as a public health tool to control typhoid fever.
authors.affiliation: Guangxi Health and Anti-Epidemic Center, Guangxi Zhuang Autonomous Region, People's Republic of China.
authors.forename: H H
authors.initials: HH
authors.lastname: Yang
authors.forename: P E
authors.initials: PE
authors.lastname: Kilgore
authors.forename: L H
authors.initials: LH
authors.lastname: Yang
authors.forename: J K
authors.initials: JK
authors.lastname: Park
authors.forename: Y F
authors.initials: YF
authors.lastname: Pan
authors.forename: Y
authors.initials: Y
authors.lastname: Kim
authors.forename: Y J
authors.initials: YJ
authors.lastname: Lee
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Xu
authors.forename: J D
authors.initials: JD
authors.lastname: Clemens
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002681:China / Q000453:epidemiology; D004196:Disease Outbreaks / Q000517:prevention & control* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D011135:Polysaccharides, Bacterial; D016016:Proportional Hazards Models; D012485:Salmonella typhi / Q000276:immunology*; D013997:Time Factors; D016896:Treatment Outcome; D014435:Typhoid Fever / Q000453:epidemiology / Q000517:prevention & control*; D014436:Typhoid-Paratyphoid Vaccines; D014611:Vaccination
chemical_list: D011135:Polysaccharides, Bacterial; D014436:Typhoid-Paratyphoid Vaccines; C057664:Vi polysaccharide vaccine, typhoid