Prevention of typhoid by Vi conjugate vaccine and achievable improvements in household WASH: Evidence from a cluster-randomized trial in Dhaka, Bangladesh.
Tadesse BT., Khanam F., Ahmed F., Im J., Islam MT., Kim DR., Kang SS., Liu X., Chowdhury F., Ahmed T., Aziz AB., Hoque M., Park J., Pak G., Zaman K., Khan AI., Pollard AJ., Kim JH., Marks F., Qadri F., Clemens JD.
BACKGROUND: Typhoid fever contributes to approximately 135,000 deaths annually. Achievable improvements in household water-hygiene-sanitation (WASH) combined with vaccination using typhoid conjugate vaccines (TCVs) may be an effective preventive strategy. However, little is known about how improved WASH and vaccination interact to lower the risk of typhoid. METHODS: 61,654 urban Bangladeshi children aged 9 months to <16 years, residing in 150 clusters with a baseline population of 205,760 residents, were randomized 1: 1 by cluster to Vi-tetanus toxoid TCV or Japanese Encephalitis (JE) vaccine. Surveillance for blood culture-confirmed typhoid fever was conducted over two years. Existing household WASH status was assessed at baseline as Better or Not Better using previously validated criteria. The reduction in typhoid risk among all residents associated with living in TCV clusters, Better WASH households, or both was evaluated using mixed-effects Poisson regression models. RESULTS: The adjusted reduced risk of typhoid among all residents living in the clusters assigned to TCV was 55% (95% confidence interval (CI): 43%,65%; p