A Cochrane review [Abstract] 1 included 18 studies with a total of over 280 000 subjects; 12 evaluated efficacy and 11 reported on adverse events. Ty21a vaccine (oral vaccine, 3 doses). According to one trial (20 543 participants), this vaccine prevents around half of typhoid cases in the first three years ((cumulative efficacy 2.5 to 3 years: 50%, 95% CI 35% to 61%; 4 trials, n=235239). Compared with placebo, there were no more vomiting, diarrhoea, nausea or abdominal pain (2 trials, n=2066), headache, or rash (1 trial, n=1190); however, fever (2 trials, n=2066) was more common.Vi polysaccharide vaccine (injection, 1 dose). This vaccine prevents around two-thirds of typhoid cases in the first year (year 1: 69%, 95% CI 63% to 74%; 99 979 participants, 3 trials; year 2: 59%, 95% CI 45% to 69%; 4 trials, n=194 969), in year 2, the trial results were more variable, with the vaccine preventing between 45% and 69% of typhoid cases. The three-year cumulative efficacy was 55% (95% CI 30% to 70%; 11 384 participants, 1 trial). Compared with placebo, there were no more fever (3 trials, n=132 261) or erythema (3 trials, n=132 261); however, swelling (3 trials, n=1 767) was more common.Vi-rEPA vaccine (2 doses). In one trial of 12 008 participants, this vaccine prevents between 50% and 96% of typhoid cases during the first two years (year 1:94%, 95% CI 75% to 99% and year 2: 87%, 95% CI 56% to 96%). Cumulative efficacy at 46 months (3.8 years) was 89% (95% CI 76% to 97%). Compared with placebo, the first and second doses of this vaccine were not associated with increased risk of adverse events. Vi-TT vaccine (two doses). The efficacy was uncertain in one trial.
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