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.