• Vaccine effectiveness
• Cost-effectiveness of typhoid Vi immunization
• Logistic feasibility of mass typhoid immunization campaign

• Indirect protection against s. typhi [ Time Frame: two years from zero time ] [ Designated as safety issue: No ]
• Overall protection against s. typhi [ Time Frame: 2 years from zero time ] [ Designated as safety issue: No ]
• Adverse event(s) following immunization [ Time Frame: 30 days from vaccination ] [ Designated as safety issue: Yes ]

• Adverse events
• Anti-Vi antibody response

This study is part of the International Vaccine Institute's (IVI's) typhoid Vi demonstration project that aims to accelerate the rational introduction of Vi vaccines in typhoid endemic countries. The purpose of this study is to determine the effectiveness of the Vi vaccine following a mass typhoid immunization campaign in an endemic area in Karachi, Pakistan. The cost-effectiveness of Vi vaccination and the logistic feasibility of a mass typhoid immunization campaign will also be evaluated.

Typhoid fever is a major cause of morbidity worldwide. The disease predominantly affects school-aged children, is more prevalent in urban areas, may last for several weeks and can lead to serious complications. Management of this disease is further complicated by the emergence of multi-drug resistant strains. Vaccination of high risk populations is considered the most promising strategy for the control of typhoid fever. The Vi polysaccharide vaccine has been targeted for accelerated introduction into public health programs due to the following reasons: it has been shown to have consistent efficacy results even in areas of high typhoid incidence; is given as a single dose; lacks patent protection and requires less strict cold chain requirements. A cluster-randomized trial involving the Vi polysaccharide vaccine and an active control (hepatitis A) was designed to determine the effectiveness and the feasibility of providing Vi vaccine under actual programmatic conditions in 3 urban slums in Pakistan. The vaccines used in this study are internationally produced and locally licensed. A complimentary, targeted, basic typhoid prevention health education program for the entire population at the initiation of the project will be provided and the actual Vi-demonstration project will be preceded by a 12-month typhoid surveillance activity.

Secondary objectives of this trial are:

• To monitor the adverse events following a routine Vi mass vaccination campaign;
• To assess the knowledge, attitudes, beliefs and practices among parents and health care providers regarding typhoid illness, treatment and prevention; and
• To study typhoid fever risk factors in the population.

A nested, prospective matched case-control study is included in the trial in order to study typhoid risk factors among children in Karachi.

• Typhoid
• Paratyphoid Fever

• Biological: Typhoid Vi vaccine
• Biological: Hepatitis A vaccine

• Experimental: Typhoid Vi polysaccharide vaccine
• Active Comparator: Inactivated Hepatitis A vaccine

• Ali M, Rasool S, Park JK, Saeed S, Ochiai RL, Nizami Q, Acosta CJ, Bhutta Z. Use of satellite imagery in constructing a household GIS database for health studies in Karachi, Pakistan. Int J Health Geogr. 2004 Sep 28;3(1):20.
• Acosta CJ, Galindo CM, Ochiai RL, Danovaro-Holliday MC, Page AL, Thiem VD, Park JK, Park E, Koo H, Wang XY, Abu-Elyazeed R, Ali M, Albert MJ, Ivanoff B, Pang T, Xu ZY, Clemens JD. The role of epidemiology in the introduction of vi polysaccharide typhoid fever vaccines in Asia. J Health Popul Nutr. 2004 Sep;22(3):240-5.

Inclusion Criteria:

• Registered in the project census
• Age: 2-16 years

Exclusion Criteria:

• Fever >37.5 degrees Celsius, axillary
• Pregnancy
• Lactating

• Aga Khan University
• The Center for Tropical Diseases, Wellcome trust
• University of Western Ontario, Canada
• GlaxoSmithKline