A cluster-randomized effectiveness trial of Vi typhoid vaccine in India.

BACKGROUND: Typhoid fever remains an important cause of illness and death in the developing world. Uncertainties about the protective effect of Vi polysaccharide vaccine in children under the age of 5 years and about the vaccine's effect under programmatic conditions have inhibited its use in developing countries. METHODS: We conducted a phase 4 effectiveness trial in which slum-dwelling residents of Kolkata, India, who were 2 years of age or older were randomly assigned to receive a single dose of either Vi vaccine or inactivated hepatitis A vaccine, according to geographic clusters, with 40 clusters in each study group. The subjects were then followed for 2 years. RESULTS: A total of 37,673 subjects received a dose of a study vaccine. The mean rate of vaccine coverage was 61% for the Vi vaccine clusters and 60% for the hepatitis A vaccine clusters. Typhoid fever was diagnosed in 96 subjects in the hepatitis A vaccine group, as compared with 34 in the Vi vaccine group, with no subject having more than one episode. The level of protective effectiveness for the Vi vaccine was 61% (95% confidence interval [CI], 41 to 75; P<0.001 for the comparison with the hepatitis A vaccine group). Children who were vaccinated between the ages of 2 and 5 years had a level of protection of 80% (95% CI, 53 to 91). Among unvaccinated members of the Vi vaccine clusters, the level of protection was 44% (95% CI, 2 to 69). The overall level of protection among all residents of Vi vaccine clusters was 57% (95% CI, 37 to 71). No serious adverse events that were attributed to either vaccine were observed during the month after vaccination. CONCLUSIONS: The Vi vaccine was effective in young children and protected unvaccinated neighbors of Vi vaccinees. The potential for combined direct and indirect protection by Vi vaccine should be considered in future deliberations about introducing this vaccine in areas where typhoid fever is endemic. (ClinicalTrials.gov number, NCT00125008.)

Emergence of tetracycline-resistant Vibrio cholerae O1 serotype Inaba, in Kolkata, India.

Out of 2,235 diarrheal stool samples collected from patients admitted to the Infectious Diseases Hospital, Kolkata, 343 cases were positive for Vibrio cholerae (341, V. cholerae O1 and 2, O139). During the year 2004, infections caused by V. cholerae serotype Ogawa and Inaba were 93 and 7%, respectively, while in 2005, the Inaba isolation rate rose to 88% as compared to 12% for Ogawa. Susceptibility to antimicrobial agents revealed that the O1 strains were resistant to multiple antibiotics (ampicillin, co-trimoxazole, furazolidone, nalidixic acid and streptomycin) with reduced susceptibility to ciprofloxacin. Increased isolation of tetracycline-resistant strains (27.3% for Ogawa and 15% for Inaba) was noted in 2005. It appears that the population might be at risk of infection by the Inaba serotype and that tetracycline may not be useful for the treatment.