Typhoid fever surveillance, incidence estimates, and progress toward typhoid conjugate vaccine introduction—worldwide, 2018–2022

Publication summary

Global estimates of typhoid fever incidence hover around 11 million to 21 million cases and 148,000 to 161,000 per year, with the greatest burden of disease in children. Surveillance for typhoid, however, is difficult, and global case numbers are estimated via a composite of different data sources. The emergence of multidrug-resistant and extensively drug-resistant strains, along with recent outbreaks, has heightened the need to improve typhoid prevention, diagnosis, and management. This US Centers for Disease Control and Prevention report highlights the issues with typhoid diagnosis and data collection, the status of resistant strains, and the experiences of countries that introduced typhoid conjugate vaccines into their national immunization campaigns and/or held mass vaccination events.

Who this is for

• Global and national health policymakers

Key findings

Global typhoid surveillance

Diagnosis and laboratory confirmation of typhoid can be difficult, as symptoms of the disease—fever, headache, diarrhea—may mimic many other childhood infections. Data collection and estimates of global incidence are usually conducted through a combination of the following:

• Laboratory-confirmed cases. When laboratory-confirmed, typhoid is usually diagnosed with blood culture, which may identify only about half of truly positive cases. The sensitivity of blood culture decreases further if the patient has already begun to take antibiotics. The capacity to perform blood culture also may not be available at many healthcare facilities and may be limited to patients presenting with severe symptoms. Despite issues with confirming typhoid cases globally, data from about 60 countries reporting to a World Health Organization (WHO) and UNICEF system revealed that confirmed case reports increased from about 8,800 in 2018 to about 1 million in 2021.
• Population-based studies. Currently, three large population-based studies collect information on typhoid incidence from Asian and African countries: 1) the Strategic Typhoid Alliance Across Africa and Asia project in Bangladesh, Malawi, and Nepal; 2) the Surveillance for Enteric Fever in Asia Project in Bangladesh, Nepal, and Pakistan; and 3) the Severe Typhoid in Africa program in Burkina Faso, Democratic Republic of the Congo, Ethiopia, Ghana, Madagascar, and Nigeria.

Drug-resistant typhoid 

Current estimates place the percentage of multidrug-resistant typhoid (typhoid resistant to chloramphenicol, ampicillin, and trimethoprim-sulfamethoxazole) at about 35% of cases in Asia and 75% of cases in Africa. Pakistan has reported significant numbers of extensively drug-resistant typhoid, which is MDR typhoid with added resistance to fluoroquinolones and third-generation cephalosporins.

Typhoid conjugate vaccine introduction

Two typhoid conjugate vaccines (TCVs)—Typbar-TCV and TYPHIVEV—have shown safety, effectiveness, and antibody response up to 7 years in children. The WHO recommends their use in routine immunization in countries with a high incidence of typhoid, also noting that vaccination programs should ideally be accompanied by improvements in sanitation, education, and typhoid case diagnosis and treatment.

Five countries, three of which represent the 44 countries and freely associated states that report high typhoid incidence, have introduced TCVs into their routine childhood immunization programs following mass vaccination and catch-up campaigns: Liberia, Nepal, Pakistan, Samoa, and Zimbabwe. Several countries combined typhoid vaccination campaigns with efforts to address malnutrition, hygiene, and need for other routine vaccinations. Of note, Samoa is the only country not to have been eligible for Gavi funding, and thus was able to offer vaccination to all regardless of age. Eleven of the 44 high-incidence countries and states are ineligible for Gavi funding to implement TCV campaigns, which may pose financial difficulty to countries deciding whether to prioritize TCV over other health investments. 

Because a lack of surveillance data may also hamper countries’ abilities to decide whether or not to implement TCV mass vaccination or routine immunization, the authors recommend informing these policy decisions with a combination of data on TCV safety and effectiveness, regional incidence or trend data from neighboring countries if available, population-based studies and/or published studies and models, outbreak reports, laboratory-confirmed case incidence if available, and case reports of issues that may be associated with severe typhoid (e.g., intestinal perforation).