Vaccine efficacy was 54.6 percent for Vi-conjugate in human infection model of Salmonella Typhi
FRIDAY, Sept. 29, 2017 (HealthDay News) — A Vi-tetanus toxoid conjugate vaccine is efficacious for prevention of typhoid fever, according to a study published online Sept. 28 in The Lancet.
Celina Jin, M.B.B.S., from the University of Oxford in the United Kingdom, and colleagues examined the efficacy of a Vi-tetanus toxoid conjugate vaccine using an established human infection model of Salmonella enterica serovar Typhi (S Typhi). Healthy adult volunteers (aged 18 to 60 years) were recruited and randomized in a 1-to-1-to-1 ratio to receive a single dose of Vi-conjugate (Vi-TT; 37 participants), Vi-polysaccharide (Vi-PS; 35 participants), or control meningococcal vaccine (31 participants). Participants orally ingested S Typhi and were assessed with daily blood culture over a two-week period.
The researchers found that 77, 35, and 35 percent of participants in the control, Vi-TT, and Vi-PS groups met the composite criteria for typhoid diagnosis, respectively, giving vaccine efficacies of 54.6 and 52 percent for Vi-TT and Vi-PS. In Vi-TT and Vi-PS participants, seroconversion was 100 and 88.6 percent, respectively; Vi-TT vaccine recipients had significantly higher geometric mean titers detected one month post-vaccination.
“Vi-TT is a highly immunogenic vaccine that significantly reduces typhoid fever cases when assessed using a stringent controlled model of typhoid infection,” the authors write. “Vi-TT use has the potential to reduce both the burden of typhoid fever and associated health inequality.”
One author disclosed ties to the pharmaceutical industry.
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