A conjugate vaccine against typhoid fever

摘要

Zulfiqar Bhutta and colleages' study in The Lancet Infectious Diseases marks an important milestone for the use of typhoid conjugate vaccines. Present Vi polysaccharide vaccines (Vi-PS) are not widely used because they cannot be given to children younger than 2 years and are thus excluded frorh the Expanded Programme of Immunization (EPI); furthermore, their effectiveness decreases rapidly after 2-3 years. Expectations of a typhoid conjugate vaccine include safe administration to children younger than 2 years, the induction of protective IgG anti-Vi immune responses, and the development of long-term, and at best lifelong, protection. Such an improved vaccine against typhoid fever could have substantial global effect in endemic regions. Bhutta and colleagues present data from their two phase 2 clinical trials of the immunogenicity and safety of conjugate typhoid vaccine Vi-CRM~197. The findings show that the vaccine was safe when given to children younger than 2 years of age, rendering it a suitable candidate for inclusion into EPI programmes. Significant post-vaccination antibody titre concentrations, although largely similar to those of the Vi-PS, were reported.