Immune responses in children after vaccination with a typhoid Vi-tetanus toxoid conjugate vaccine in Bangladesh

AUTHORS

Farhana Khanam, Golap Babu, Nazia Rahman, Xinxue Liu, Nazmul Hasan Rajib, Shams Uddin Ahmed, Md Ismail Hossen, Prasanta Kumar Biswas, Sarah Kelly, Katherine Thesis-Nyland, Yama Mujadidi, Nigel A J McMillan, Andrew J Pollard, John D Clemens, Firdausi Qadri

ABSTRACT

A cluster-randomized trial of Vi-TT was conducted in Dhaka, Bangladesh, using JE vaccine as the control. A subset of 1,500 children were randomly selected on 2:1 basis (Vi-TT vs JE) to assess immune response. Blood was collected before vaccination, and on days 28, 545 and 730 post-vaccination and plasma anti-Vi-IgG response was measured. A robust, persistent antibody response was induced after single dose of Vi-TT, even after 2 years of vaccination. While there is no accepted serological antibody threshold of protection, analyzing the antibodies of children who received Vi-TT provides evidence that may later be useful in predicting population protection.

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