What is the efficacy of Vi capsular polysaccharide (ViCPS) antigen vaccine used in the prevention of typhoid fever (enteric fever)?

Updated: Aug 19, 2019
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

A systemic review and meta-analysis of 5 randomized controlled trials on the efficacy and safety of ViCPS versus placebo or nontyphoid vaccine found a cumulative efficacy of 55% (95% CI, 30%-70%).

The efficacy of vaccination with ViCPS has not been studied among persons from areas without endemic disease who travel to endemic regions or among children younger than 5 years. ViCPS has not been given to children younger than 1 year.

Questions concerning Vi typhoid vaccine effectiveness in young children (ie, < 5 y) have inhibited its use in developing countries. Whether the vaccine is effective under programmatic conditions is also unclear.

Sur et al conducted a phase IV effectiveness trial in slum-dwelling residents aged 2 years or older in India to determine vaccine protection. Participants (n=37,673) were randomly assigned to receive a single dose of either Vi vaccine or inactivated hepatitis A vaccine, according to geographic clusters. The mean rate of Vi vaccine coverage was 61% and 60% for the hepatitis A vaccine.

Typhoid fever was diagnosed in 96 subjects in the hepatitis A vaccine group compared with 34 in the Vi vaccine group (no more than 1 episode was reported per individual). Protective effect for typhoid with the Vi vaccine was 61% (P< 0.001) compared with the hepatitis A vaccine group. Children vaccinated while aged 2-5 years had an 80% protection level. Unvaccinated members of the Vi vaccine clusters showed a protection level of 44%. The overall protection level with all Vi vaccine cluster residents was 57%. The authors concluded that the Vi vaccine was effective in young children and protected unvaccinated neighbors of Vi vaccinees. [74]


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