No currently available vaccines against typhoid are meant for children younger than 2, but a new conjugate vaccine manufactured by India’s Bharat Biotech as Typbar-TCV could change that.
Following a recent meeting, the World Health Organization’s Strategic Advisory Group of Experts (SAGE) on Immunization recommended (PDF) the capsular Vi-polysaccharide conjugate vaccine for infants and children over 6 months in typhoid endemic regions. The group further said catch-up immunizations for those under 15 years old should begin, depending on local disease prevalence.
The expert panel based its decision on a recent phase 2b trial carried out by the University of Oxford, the first efficacy trial on the vaccine. All together, investigators split 112 healthy adults in the U.K. into three groups that received either Bharat Biotech’s shot, Sanofi Pasteur’s nonconjugated version called Typhim Vi or placebo. To save time waiting for subjects to contract the disease naturally, the trial used a “controlled human infection" model, where volunteers were deliberately infected with the pathogen, or in this case, live typhoid bacteria.
As results published in The Lancet show, the vaccine halved the total number of infections, and researchers estimated that its efficacy could reach as high as 87% under an alternative definition of typhoid fever.
In a statement quoted by Livemint following the study, Bharat Biotech said its vaccine "can be administered to children below two years of age and does confer long-term immunity.” The vaccine is currently approved in India, with applications underway in several other countries.
The WHO has so far recommended two types of typhoid vaccines. Sanofi’s Typhim Vi and GlaxoSmithKline’s Typherix are one-dose inactivated vaccines for those over 2 years old. A three- or four-dose oral regimen produced by PaxVax as Vivotif should not be given to children under 6.
“Not only could this vaccine save lives, it could also prove to be a valuable weapon in the fight against antimicrobial resistance,” Seth Berkley, head of international nonprofit body Gavi, the Vaccine Alliance, said, as quoted by the BBC. Antibiotic resistance poses a growing threat around the globe, highlighting the importance of prevention efforts.
According to the most recent estimates from WHO, the bacteria infects about 21 million people annually—mainly through ingestion of contaminated food or water—and kills about 222,000 each year.
Recommendations from SAGE are one of the criteria used by WHO for making decisions on prequalification, which would allow for international organizations like UNICEF to procure the vaccine. Livemint reported that the Indian vaccinemaker is currently seeking a spot on the WHO program.