BackgroundSalmonella Typhi is a major cause of fever in children in low- and middle-income countries. The recently WHO prequalified typhoid conjugate vaccine (TCV) was shown to be efficacious in a human challenge model but no efficacy trials in endemic populations have been completed.MethodsIn this phase III participant- and observer-blinded randomized controlled trial in Lalitpur, Nepal, children aged 9 months to <16 years of age, were randomized 1:1 to receive either TCV or a capsular group A meningococcal conjugate vaccine (Men A) as control. The primary endpoint was blood culture-confirmed typhoid fever. Study follow-up continues for 2 years; here we present the interim analysis after 12 months of follow-up, for safety, immunogenicity and efficacy.Results10,005 participants received TCV and 10,014 received Men A. Blood culture-confirmed typhoid fever occurred in 7 participants who received TCV and 38 receiving Men A; vaccine efficacy: 81.6% (95% CI, 58.8%, 91.8%, P<0.001). 132 SAEs occurred in the first 6 months with one (pyrexia) identified as vaccine-related. The participant remains blinded. Seroconversion (≥ four-fold rise in Vi-IgG 28 days after vaccination) was 99% in the TCV group (N=677/683) and 2% in the control group (N=8/380).ConclusionA single dose of TCV is safe, immunogenic, and effective, and the deployment of the vaccine will reduce the burden of typhoid in high-risk populations. This new evidence of efficacy is especially timely with the recent spread of extensively drug resistant typhoid fever which threatens child health in affected regions.Trial registration numberISRCTN43385161

NDM-producing Klebsiella pneumoniae strains represent major clinical and infection control challenges, particularly in resource-limited settings with high rates of antimicrobial resistance. Determining whether transmission occurs at a gene, plasmid, or bacterial strain level and within hospital and/or the community has implications for monitoring and controlling spread. Whole-genome sequencing (WGS) is the highest-resolution typing method available for transmission epidemiology. We sequenced carbapenem-resistant K. pneumoniae isolates from 26 individuals involved in several infection case clusters in a Nepali neonatal unit and 68 other clinical Gram-negative isolates from a similar time frame, using Illumina and PacBio technologies. Within-outbreak chromosomal and closed-plasmid structures were generated and used as data set-specific references. Three temporally separated case clusters were caused by a single NDM K. pneumoniae strain with a conserved set of four plasmids, one being a 304,526-bp plasmid carrying blaNDM-1. The plasmids contained a large number of antimicrobial/heavy metal resistance and plasmid maintenance genes, which may have explained their persistence. No obvious environmental/human reservoir was found. There was no evidence of transmission of outbreak plasmids to other Gram-negative clinical isolates, although blaNDM variants were present in other isolates in different genetic contexts. WGS can effectively define complex antimicrobial resistance epidemiology. Wider sampling frames are required to contextualize outbreaks. Infection control may be effective in terminating outbreaks caused by particular strains, even in areas with widespread resistance, although this study could not demonstrate evidence supporting specific interventions. Larger, detailed studies are needed to characterize resistance genes, vectors, and host strains involved in disease, to enable effective intervention.

IntroductionInvasive infections caused by Salmonella enterica serovar Typhi and Paratyphi A are estimated to account for 12–27 million febrile illness episodes worldwide annually. Determining the true burden of typhoidal Salmonellae infections is hindered by lack of population-based studies and adequate laboratory diagnostics.The Strategic Typhoid alliance across Africa and Asia study takes a systematic approach to measuring the age-stratified burden of clinical and subclinical disease caused by typhoidal Salmonellae infections at three high-incidence urban sites in Africa and Asia. We aim to explore the natural history of Salmonella transmission in endemic settings, addressing key uncertainties relating to the epidemiology of enteric fever identified through mathematical models, and enabling optimisation of vaccine strategies.Methods/designUsing census-defined denominator populations of ≥100 000 individuals at sites in Malawi, Bangladesh and Nepal, the primary outcome is to characterise the burden of enteric fever in these populations over a 24-month period. During passive surveillance, clinical and household data, and laboratory samples will be collected from febrile individuals. In parallel, healthcare utilisation and water, sanitation and hygiene surveys will be performed to characterise healthcare-seeking behaviour and assess potential routes of transmission. The rates of both undiagnosed and subclinical exposure to typhoidal Salmonellae (seroincidence), identification of chronic carriage and population seroprevalence of typhoid infection will be assessed through age-stratified serosurveys performed at each site. Secondary attack rates will be estimated among household contacts of acute enteric fever cases and possible chronic carriers.Ethics and disseminationThis protocol has been ethically approved by the Oxford Tropical Research Ethics Committee, the icddr,b Institutional Review Board, the Malawian National Health Sciences Research Committee and College of Medicine Research Ethics Committee and Nepal Health Research Council. The study is being conducted in accordance with the principles of the Declaration of Helsinki and Good Clinical Practice. Informed consent was obtained before study enrolment. Results will be submitted to international peer-reviewed journals and presented at international conferences.Trial registration numberISRCTN 12131979.Ethics referencesOxford (Oxford Tropical Research Ethics Committee 39-15).Bangladesh (icddr,b Institutional Review Board PR-15119).Malawi (National Health Sciences Research Committee 15/5/1599).Nepal (Nepal Health Research Council 306/2015).