Understanding Typhoid: Generating Evidence for Action
Typhoid is a common illness across much of Southeast Asia, where the bacterial disease spreads through contaminated food and water. The disease sickens and kills thousands of people in Southeast Asia each year, contributing to more than 128,000 deaths annually from typhoid-related illnesses worldwide, but a new type of typhoid vaccine has the potential to significantly reduce the incidence of typhoid in communities most affected. Countries across Southeast Asia are now looking to introduce the vaccine, but before they can establish vaccine introduction guidelines, first they need current, accurate data on where and at what age people are affected by the disease. Knowing the burden of typhoid – and knowing where and at what age people are affected – will help decision makers across Southeast Asia implement better evidence- based public health measures and plans for vaccine introduction.
Sabin launched the Surveillance for Enteric Fever in Asia Project (SEAP) in 2014 to estimate the burden of typhoid in three countries in Southeast Asia: Bangladesh, Pakistan and Nepal. Data generated by the study, which is funded by the Bill & Melinda Gates Foundation, will help decision makers create informed and targeted health policies regarding typhoid, facilitating the assessment of interventions and increasing public understanding of the disease. This data will also enable decision makers to better understand the broader impact of typhoid, including the cost of illness and the most common risk factors facing communities.
In partnership with local hospitals, laboratories, researchers and health officials, SEAP is collecting data through a number of different surveillance mechanisms to make sure that the study’s findings are as accurate and comprehensive as possible. These mechanisms include hospital- and laboratory-based surveillance; household surveys; economic evaluation of direct and indirect costs for patients; blood sample storage; and patient follow-up six weeks after illness to capture information on relapse, morbidity and mortality. By factoring together all of these components, SEAP is able to both address the long-unanswered questions about typhoid incidence in the three countries and inform global policy decisions on typhoid prevention and the introduction of a new type of typhoid vaccine.
SEAP is already having a major impact, as evidenced by the study’s role in updating global recommendations for the use of typhoid vaccines. Typhoid vaccines have existed since the late 1900s, but until recently, they were not highly effective and could not be given to young children, who experience the greatest burden of typhoid. A new type of typhoid vaccine, known as typhoid conjugate vaccines, offer advantages over previously available vaccines, including the ability to provide longer-lasting protection and to be administered to children younger than two years of age – making them the first-ever approved for this at-risk age group.
In March 2017, Sabin delivered more than 15,000 data records from SEAP to the World Health Organization (WHO) to help typhoid experts from around the globe to evaluate the benefits of introducing new typhoid conjugate vaccines. A few months later, Gavi, the Vaccine Alliance also reviewed SEAP data before deciding to dedicate $85 million to help low-income countries introduce the typhoid conjugate vaccine. After considering all the available evidence, in early 2018 the WHO updated its recommendations for typhoid vaccine use, approving the first typhoid conjugate vaccine for introduction worldwide.
Sabin continues to collect and analyze data through SEAP in Bangladesh, Pakistan and Nepal, to help inform future policy decisions both in the region and worldwide. As of June 2018, SEAP has screened more than 27,000 patients in the three countries. By September 2019, Sabin expects to have enrolled more than 6,000 people in the study – the most ever enrolled in a typhoid surveillance study.
Data generated by SEAP not only establishes the burden of disease, fatality rate and complications, but also provides baseline measures for vaccine effectiveness studies and use in assessments of other prevention and control measures. Additionally, the study includes the development of a biobank of Salmonella strains for use in future research, including studies designed to assess the development of drug resistance, one of the greatest threats to typhoid treatment.
Sabin’s efforts to improve typhoid surveillance come at a critical time in Southeast Asia, as rates of dangerous, drug-resistant typhoid increase across the region. Findings from SEAP will be crucial for targeting future prevention and control interventions in these countries, and protecting the health of millions of people worldwide currently at risk of this vaccine-preventable disease.