Vi-tetanus toxoid conjugate vaccine protects kids from typhoid fever, large study finds
Click Here to Manage Email Alerts
A single dose of Vi-tetanus toxoid conjugate vaccine provided protection against typhoid fever in children aged 9 months to 16 years, according to data from a large study published in The Lancet.
Vi-tetanus toxoid conjugate vaccine (Vi-TT) is recommended by WHO in high-burden countries, “but there is little evidence about its ability to protect against clinical typhoid in such settings,” Kathleen M. Neuzil, MD, MPH, FIDSA, professor of vaccinology and director of the Center for Vaccine Development and Global Health at the University of Maryland School of Medicine, and colleagues wrote.
“This study is big news — a single-dose typhoid conjugate vaccine was highly effective in preventing typhoid in children of all ages, including those younger than 2 years of age,” Neuzil told Healio.
Neuzil and colleagues conducted a participant- and observer-masked trial in in Dhaka, Bangladesh, in which 150 clusters that each contained around 1,350 people were randomly assigned at a 1:1 ratio to receive either the Vi-TT vaccine or the SA 14-14-2 Japanese encephalitis vaccine.
Overall, the trial vaccinated more than 60,000 children aged 9 months to 16 years between April 2018 and May 2019.
According to Neuzil and colleagues, the incidence rate of typhoid fever in the Vi-TT vaccine group was 96 cases per 100,000 years compared with 635 cases per 100,000 person years in the control group, demonstrating that the Vi-TT vaccine conferred 85% total protection against typhoid fever (97.5% CI, 76%-91%).
Total protection did not differ significantly among age groups, the authors reported. The rate was 81% among participants aged younger than 2 years, 80% among those aged 2 to 4 years, and 88% among those aged 5 to 16 years (all three-point estimates — 95% CI, 80%-88%).
“While we anticipated conjugate vaccines would be effective in this age young group — similar to pneumococcal, Haemophilus influenzae type b and meningococcal conjugate vaccines — this is the first clinical trial evidence of such,” Neuzil said. “WHO recommends all typhoid-endemic countries introduce typhoid conjugate vaccines beginning at 9 months of age.”
In a related editorial, Prof. John A. Crump, MD, MBChB, DTM&H, and PhD candidate Win Thandar Oo, BS, MB, MMedSc, from the University of Otago in New Zealand, said smaller studies conducted in Nepal and Malawi saw similar results.
“Collectively these trials show that Vi-TT provides a high degree of protection across distinct geographical settings up to 18 months of follow-up,” Crump and Oo wrote. “Continued follow-up of participants is needed to understand longer term efficacy, including whether booster doses might be needed.”
References:
Qadri F, et al. Lancet. 2021;doi:10.1016/S0140-6736(21)01124-7.
Crump JA, Oo WT. Lancet. 2021;doi:10.1016/S0140-6736(21)01340-4.