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 Kolkata, India. The cost-effectiveness of the 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 since 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.

This project attempts to evaluate a new vaccination strategy for residents of endemic areas. 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 2 contiguous urban wards in Kolkata. The vaccines used in this study are internationally produced and locally licensed. A 1 year pilot phase will precede the actual Vi-demonstration project. Surveillance for typhoid fever cases will continue after the mass immunization campaign. A passive surveillance system to evaluate adverse events following immunization will be implemented. Socio-economic studies will be conducted in parallel to the effectiveness evaluation. The knowledge, attitudes, beliefs and practices among parents and health care providers regarding typhoid illness, treatment and prevention will be assessed. Logistic, feasibility and vaccine costs will also be determined.

Inclusion Criteria:

• Registered in the project census
• Age >=2 years
• Provide informed consent to receive vaccine

Exclusion Criteria:

• Fever (>37.5 degrees Celsius)
• Pregnancy
• Lactating