One-third of the world’s population is at risk of contracting typhoid, a systemic bacterial infection spread through contaminated food and water that kills more than 128,000 people each year, primarily children in low-income countries. Caused by Salmonella enterica serotype Typhi (S. Typhi), typhoid is an acute illness that is often misdiagnosed because its symptoms – prolonged fever, headache, nausea, constipation, loss of appetite and diarrhea – are so common.

Newly developed typhoid conjugate vaccines have the potential to dramatically reduce the burden of typhoid around the world. These vaccines offer important advantages over previously available typhoid vaccines, including longer duration of protection, fewer doses required and the ability to protect children under two years of age, which allows for typhoid conjugate vaccines to be delivered with other vaccines in routine immunization of infants. By reducing the burden of typhoid, typhoid conjugate vaccines also have the potential help to prevent the occurrence of drug resistance. A recent rise in multidrug-resistant typhoid and nontyphoidal Salmonella has increased the urgent need for more effective vaccines.

In March 2018, the World Health Organization recommended the introduction of the typhoid conjugate vaccines for infants and children over six months of age in typhoid-endemic countries. This new policy will help ensure access to typhoid vaccination in communities most impacted by the disease, which is responsible for more than 12.5 million infections a year.

To speed the introduction of these life-saving vaccines, additional research and scientific collaboration is required.

Establishing Burden of Disease

Since 2014, Sabin has led a large, landmark surveillance study in Bangladesh, Nepal and Pakistan. The Surveillance for Enteric Fever in Asia Project (SEAP) collects data to establish the burden of enteric fever, the current trends of antimicrobial resistance and the cost of typhoid and paratyphoid on families, communities and countries’ healthcare systems. Data from the study have informed global decisions on typhoid conjugate vaccine policy and are being used to support country-level decision making to introduce typhoid conjugate vaccines into the national routine immunization schedule. Read Sabin’s blog on SEAP’s impact.

Typhoid surveillance currently depends on blood culture testing, which is expensive and requires specialized personnel and laboratory facilities to perform. However, policymakers need to be aware of the disease burden in communities outside of major cities, where the use of blood culture diagnostics is often not possible. To address this limitation, Sabin is leveraging the research network established for SEAP to identify more cost-effective mechanisms for conducting enteric fever surveillance. The Sero-Epidemiology & Environmental Surveillance (SEES) study, launched in January 2019, has begun collecting data to inform the development of population-based serological and environmental surveillance tools to estimate disease burden. Through this study, we plan to validate potential low-cost surveillance tools as an alternative to blood culture testing and investigate community water testing to detect the presence of bacteria.

Promoting Collaboration

Since 2010, Sabin has provided a platform for stakeholders to guide typhoid vaccine policy and prepare for the introduction of new vaccines. Sabin’s Coalition against Typhoid hosts international conferences on typhoid and other invasive salmonelloses, convening scientists and researchers from around the world to present new research and promote collaboration. As typhoid conjugate vaccines are reviewed and introduced, Sabin will work with stakeholders to support advocacy efforts for uptake and implementation of expanded immunization programs.

In October 2017, Sabin’s Coalition against Typhoid joined forces with the Typhoid Vaccine Acceleration Consortium (TyVAC). Together, the Coalition and TyVAC are working to focus attention on typhoid and the need for typhoid conjugate vaccines and water, sanitation, and hygiene interventions to reduce the burden and impact of typhoid fever. Learn more about the joint effort to take on typhoid on our website.