Typhoid Vi Vaccine Effectiveness in a Population Older Than 5 Years of Age Living in an Endemic Area in Hechi, Guangxi, P.R. China: A Group-Randomized Controlled Demonstration Project

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.

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 (meningococcal A vaccine) was designed to determine the effectiveness and the feasibility of providing Vi vaccine under actual programmatic conditions in 2 populous townships of Hechi City. The vaccines used in this study are locally produced and licensed in China. 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.

Secondary objectives of this trial are:

• To estimate the logistic feasibility of a mass typhoid immunization campaign
• To assess the knowledge, attitudes, beliefs and practices among parents and health care providers regarding typhoid illness, treatment and prevention
• To study typhoid fever risk factors in the population