Typhoid fever vaccines: systematic review and meta-analysis of randomised controlled trials

Abstract

We undertook a systematic review and meta-analysis of randomised controlled trials comparing a typhoid fever vaccine with any alternative typhoid fever vaccine or inactive agent. Trials evaluating killed whole-cell vaccines were excluded. The cumulative efficacy at 3 years for the Ty21a and the polysaccharide Vi vaccine were similar: 51% (95%CI 36%, 62%), and 55% (95%CI 30%, 70%), respectively. The cumulative efficacy of the Vi-rEPA vaccine at 3.8 years was higher, 89% (95%CI 76%, 97%), but this vaccine has not yet been licensed for use and was evaluated in only one trial. Adverse events were mild in nature and for most, not significantly more frequent in any of the vaccine groups when compared with placebo. Both the currently licensed Ty21a and Vi vaccine, are safe and efficacious for preventing typhoid fever. Neither vaccine is currently registered for administration to children below 2 years of age. Given the recent finding that typhoid fever also affects infants, development of a conjugate vaccine is warranted.