Protection conferred by typhoid fever against recurrent typhoid fever in urban Kolkata.

• Published in: PLOS Neglected Tropical Diseases
• Main Authors: Justin Im, Md Taufiqul Islam, Deok Ryun Kim, Faisal Ahmmed, Yun Chon, K Zaman, Ashraful Islam Khan, Mohammad Ali, Dipika Sur, Suman Kanungo, Shanta Dutta, Sujit K Bhattacharya, Gordon Dougan, Kathryn E Holt, Florian Marks, Jerome H Kim, Firdausi Qadri, John D Clemens
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2020
• Subjects: Arctic medicine. Tropical medicine; RC955-962; Public aspects of medicine; RA1-1270; Arctic
• Online Access: https://doi.org/10.1371/journal.pntd.0008530; https://doaj.org/article/2bcae212f962459a8fbdd1251fcddf60

We evaluated the protection conferred by a first documented visit for clinical care of typhoid fever against recurrent typhoid fever prompting a visit. This study takes advantage of multi-year follow-up of a population with endemic typhoid participating in a cluster-randomized control trial of Vi capsular polysaccharide typhoid vaccine in Kolkata, India. A population of 70,566 individuals, of whom 37,673 were vaccinated with one dose of either Vi vaccine or a control (Hepatitis A) vaccine, were observed for four years. Surveillance detected 315 first typhoid visits, among whom 4 developed subsequent typhoid, 3 due to reinfection, defined using genomic criteria and corresponding to -124% (95% CI: -599, 28) protection by the initial illness. Point estimates of protection conferred by an initial illness were negative or negligible in both vaccinated and non-vaccinated subjects, though confidence intervals around the point estimates were wide. These data provide little support for a protective immunizing effect of clinically treated typhoid illness, though modest levels of protection cannot be excluded.