Countries with a high incidence of typhoid or antimicrobial resistance to Salmonella Typhi should introduce vaccinations, according to the World Health Organization’s (WHO) Strategic Advisory Group of Experts (SAGE) on Immunization.

SAGE also recommended routine COVID-19 vaccination for groups at highest risk of severe COVID-19 disease every six months and reducing polio vaccines from three to two doses in countries at low risk.

SAGE, which meets every quarter, spent last week considering global reports on emerging disease challenges and setting priorities in a context where countries are facing “uncertain funding, competing priorities and eroding public trust”, said chair ​​Professor Anthony Scott.

“Typhoid fever is estimated to cause about six million cases and 72,000 deaths worldwide,” said Scott, who is professor of vaccine epidemiology at the London School of Hygiene and Tropical Medicine.

“Children between five and nine years of age are most likely to have laboratory-confirmed typhoid fever and thus carry the largest share of cases,” said Scott, adding that protection from a single dose of typhoid conjugate vaccine (TCV) can decrease over time, particularly in children under two.

SAGE is thus also recommending a booster dose for children aged around five years of age in very high typhoid incidence settings.

SAGE first recommended rolling out the TCV in 2018, said Scott, so many high incidence countries have “already either implemented or have set in train the process of implementing the vaccine”.

In Southeast Asia, Pakistan, Nepal, Bangladesh and India are considering the vaccine. In Africa, Zimbabwe, Kenya and Niger, are also considering the vaccine, said Scott.

However, he warned that “the epidemiology of the disease varies quite widely, even within country, and it’s a particularly difficult disease to characterise and diagnose.”

COVID-19 vaccines for vulnerable groups

“While the global burden of severe COVID-19 has declined worldwide thanks to broad immunity, both from vaccine and past infection, the virus continues to cause significant illness and death,” said Scott.

SAGE recommends COVID-19 vaccination every six months for groups at highest risk of severe disease – the elderly, older adults with significant comorbidities or severe obesity, residents in care homes and and moderately or severely immunocompromised individuals. 

SAGE also recommends one dose for pregnant women, ideally during the second trimester.

However, Dr Kate O’Brien, head of the WHO’s Department of Immunization, Vaccines and Biologicals, acknowledged that country support from the vaccine platform, Gavi, to buy COVID-19 vaccines had ended last year which would impact on the availability of these vaccines.

Dr Annelies Wilder-Smith, WHO Vaccine Policy Team Lead and SAGE Executive Secretary, added that while the current COVID-19 vaccines prevented severe disease, the weakness was that they did not prevent transmission.

“To reduce transmission, we would really like to see vaccines that have an impact on mucosal immunity,” said Wilder-Smith.

Reduction in polio doses

Wild polio virus transmission remains endemic in only two countries, Pakistan and Afghanistan. 

“SAGE is deeply concerned about the continued transmission of wild polio virus type one in both of these countries, as well as disruptions that are hindering the shipment and laboratory testing of stool and environmental samples from Afghanistan,” said Scott.

Circulating vaccine-derived polio virus type two had also been detected in “several African countries”, including northern Nigeria and Somalia.

“There’s an urgent need to strengthen routine immunisation and reach zero dose children, to curb circulating vaccine-derived polio virus type two transmission,” Scott stressed.

But in countries at low risk of polio, it is possible to reduce the number of bivalent polio doses from three to two, “provided this combined schedule will sustain mucosal immunity”.

Acute resource reductions

O’Brien acknowledged the current context of conflicts, and economic challenges, resulting in  national health budgets being reduced.

The challenge for countries’ National Technical Advisory Groups on vaccines is to ensure that they have the surveillance systems to know where diseases occur and where the target should be, she said.

“The focus of 2026 and onward is to protect the core of the core of immunisation programmes and to integrate the efforts across different initiatives and for countries to make decisions on where they will focus the resources,” said O’Brian.

However, she noted that the WHO recommended vaccinations for 14 diseases, and over 80% of countries cover 10 or more of those diseases.

“This has been an incredible success story that has allowed for health impact and health gains to be made, including the reduction of infant mortality. But we’re entering a very challenging phase, and countries will need to make increasing decisions on optimization of their vaccine schedules,” she warned.