Salmonella Typhi Vi polysaccharide conjugate vaccine protects infants and children against typhoid fever

The past decade has seen remarkable progress in our understanding of the scale of the global typhoid fever problem,1 the alarming emergence in south Asia of extensively drug-resistant Salmonella enterica serovar Typhi (S Typhi) threatening effective treatment,2 and the WHO prequalification of a typhoid conjugate vaccine,3 a new tool to prevent disease. In The Lancet, Firdausi Qadri and colleagues report the analysis to 18 months of follow-up of a cluster-randomised trial of the WHO prequalified S Typhi Vi polysaccharide tetanus toxoid conjugate vaccine (Vi-TT; Tybar TCV, Bharat Biotech International, Hyderabad, India) among infants and children aged 9 months to younger than 16 years in the densely populated and highly mobile urban area of Mirpur, Dhaka, Bangladesh.4 Compared with the SA 14-14-2 Japanese encephalitis vaccine control group, Vi-TT conferred 85% (97·5% CI 76–91, p