New generation typhoid vaccines: an effective preventive strategy to control typhoid fever in developing countries.

Typhoid fever is a serious systemic infection, caused by the enteric pathogen Salmonella enterica serovar Typhi, a highly virulent and invasive enteric bacterium. This disease occurs in all parts of world where water supplies and sanitation are substandard. These pathogens then travel to food, drinks and water through house-flies and other vectors. Globally, an estimated 12-33 million cases of enteric fever occur with 216,00-600,000 deaths per year, almost exclusively in the developing countries. Health surveys conducted by the Health Ministry of India in the community development areas indicated a morbidity rate varying from 102-2219/100,000 population in different parts of the country. A limited study in an urban slum showed 1% of children up to 17 years of age suffer from typhoid fever annually. The continued high burden of typhoid fever and the alarming spread of antibiotic resistant strains led the World Health Organization (WHO), almost ten years ago, to recommend immunization using the two new-generation vaccines in school- aged children in areas where typhoid fever posed a significant problem and where antibiotic resistant strains were prevalent. Morbidity and mortality due to high incidence of typhoid fever favors the introduction of typhoid vaccine in routine immunization in India. This vaccine should be given at the age of 2 years with Vi antigen vaccine and at least one more dose be given at 5 years of age.