WHO Updates Typhoid Vaccine Guidance

Typhoid conjugate vaccine (TCV) is now the preferred option for routine immunisation in typhoid-endemic countries, with updated guidance placing greater emphasis on local incidence, antimicrobial resistance and the durability of protection. WHO’s 2026 position paper replaces its 2018 guidance and reflects new evidence from vaccine introductions, longer follow-up and booster-dose studies. The recommendations retain vaccination within a wider prevention strategy that also includes water, sanitation and hygiene, food safety, health education and improved diagnosis and treatment. The updated approach gives countries more flexibility over age at vaccination while adding clearer circumstances in which a booster dose should be considered. 

Routine Schedules Adapt to Local Risk 

WHO recommends TCV for routine programmes in endemic countries because of its immunological properties, suitability for young children, longer protection and programme advantages over Vi polysaccharide and oral Ty21a vaccines. In settings with high or very high incidence, a high case fatality ratio or a high burden of antimicrobial-resistant Salmonella Typhi, the first dose is recommended at 9–24 months. Medium-incidence settings may also consider TCV, particularly where case fatality or antimicrobial resistance is high. In these settings, vaccination can begin from 2 years and may be delayed to 5 years according to local epidemiology and feasibility. 

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Catch-up vaccination is recommended when TCV is introduced. The age range should reflect disease patterns and programme feasibility, although children under 15 years are often targeted where burden and delivery conditions support this approach. Vaccinating several age cohorts at introduction is expected to accelerate disease impact, with available evidence showing indirect protection. Older children and adults may also be considered according to local epidemiology and product licensure. 

The guidance adds a more defined role for booster vaccination. Countries with very high incidence should consider a dose around 5 years for children first vaccinated at 9–24 months. In high-incidence settings, a booster may be considered when protection is waning, while it may be unnecessary where waning is limited, particularly if the primary dose is given at age 2 years or later. Lack of booster-delivery capacity should not prevent TCV introduction. 

Evidence Supports Strong Protection but Variable Durability 

TCVs produce robust anti-Vi antibody responses, including in infants and young children, with antibody concentrations that are higher and more sustained than after Vi polysaccharide vaccines. Randomised trials in Malawi, Nepal and Bangladesh demonstrated vaccine efficacy, while programme and outbreak-response assessments generally reported effectiveness against blood culture-confirmed typhoid ranging from approximately 70% to above 90%. Post-introduction evaluations in several countries also found reduced typhoid incidence in vaccinated age groups, although programme follow-up remains shorter than long-term trial extensions. 

Longer follow-up has shown that protection does not wane uniformly. In Malawi, efficacy remained stable through 4.61 years. By contrast, data from Nepal and Bangladesh showed declining protection over longer periods, particularly among children vaccinated at younger ages. WHO therefore bases booster policy on epidemiological setting, age at primary vaccination, observed waning, cost-effectiveness and programme feasibility rather than recommending a booster universally. 

Safety evidence remains favourable. Randomised trials, systematic reviews and post-licensure surveillance found no increased risk of serious adverse events compared with control vaccines or placebo, although some comparisons were limited by small numbers of events. Passive surveillance reports also cannot establish causality. Available data indicate that repeat and booster dosing is well tolerated. Licensed TCVs are considered interchangeable on the basis of immunobridging data and any recommended TCV may be used for primary and booster doses. 

Guidance Extends to Outbreaks and Special Populations 

Countries experiencing typhoid outbreaks should consider introducing TCV or strengthening existing routine immunisation. Vaccination may also be used in large or prolonged outbreak-response campaigns, although WHO notes that evidence is limited and there is no official definition of an outbreak or threshold for vaccine use. Decisions should account for vaccine availability, logistics and costs as well as antimicrobial resistance, outbreak size and duration and the ages affected. Vaccination should accompany case management and improvements in water, sanitation and hygiene rather than replace them. 

Typhoid vaccination may also be considered in fragile, conflict-affected and vulnerable settings where disease risk is high, especially when other interventions cannot be implemented rapidly. For pregnancy and breastfeeding, direct safety data remain limited, but WHO identifies no theoretical safety concerns for TCV or Vi polysaccharide vaccines and states that they may be used. The live attenuated Ty21a vaccine should be avoided during pregnancy. Immunocompromised people, including those living with HIV, should receive TCV, while Ty21a should not be used in uncontrolled HIV. 

Surveillance is central to the updated approach. Endemic countries are advised to strengthen systems capable of confirming typhoid by blood culture or polymerase chain reaction, tracking vaccine impact and detecting waning immunity and antimicrobial resistance. Research priorities include better evidence on single-dose durability, booster timing and impact, outbreak vaccination, correlates of protection and methods for estimating typhoid incidence where routine surveillance is limited. 

The 2026 guidance reinforces TCV as the main vaccine for routine typhoid control while moving towards schedules that respond more closely to local epidemiology and observed durability. Early vaccination and catch-up remain central where disease burden, mortality or antimicrobial resistance are high, but booster use is targeted rather than automatic. WHO also extends the framework to outbreaks, vulnerable settings and special populations while stressing that vaccination sits alongside sanitation, food safety, surveillance and effective clinical management. Remaining uncertainties around waning protection, optimal booster timing and outbreak use continue to shape research priorities and future programme decisions. 

Source: World Health Organization 

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