ArticleInternational journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases2024
Longevity of immune response after a single dose of typhoid conjugate vaccine against Salmonella Typhi among children in Hyderabad, Pakistan.
Article in International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases, 2024. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 8 papers, 1 of them a synthesis that pooled it.
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Who cites it
8 citing papers in PubMed, 1 synthesis or guideline pooled it.
- Efficacy, immunogenicity, and safety of typhoid conjugate vaccines in children and adolescents: a systematic review and meta-analysis.Infection · 2026Pooled it
- Review
- Article
- Modeling the initial impact and predicted future benefits of TCV from two Pakistani provinces.The Lancet regional health. Southeast Asia · 2025Article
- Assessing Salmonella Typhi Pathogenicity and Prevention: The Crucial Role of Vaccination in Combating Typhoid Fever.International journal of molecular sciences · 2025Review
- Immunogenicity and reactogenicity of a booster dose of a typhoid conjugate vaccine (TCV) in Malawian pre-school children.EClinicalMedicine · 2025Article
- WHO preferred product characteristics for bivalent Salmonella Typhi/Paratyphi A vaccine for comprehensive protection against enteric fever- key considerations and research gaps.Gates open research · 2025Review
- Emergence of carbapenem-resistantFrontiers in microbiology · 2025Article
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Abstract
objectivesTyphoid remains a persistent contributor to childhood morbidity in communities lacking sanitation infrastructure. Typhoid conjugate vaccine (TCV) is effective in reducing disease risk in vaccinees; however, the duration of protection is unknown. This study measured the longevity of immune response to TCV in children aged under 10 years in Hyderabad, Pakistan, where an outbreak of extensively drug-resistant typhoid has been ongoing.
methodsA subset of children who received the TCV as part of the outbreak response were enrolled purposively from March 2018 to February 2019. The participants were followed up until January 2023. Blood samples were taken at baseline, 4-6 weeks, 6 months, and annually 1-4 years after vaccination to measure anti-Vi immunoglobulin (Ig) G levels using enzyme-linked immunosorbent assay. Active phone-based surveillance was performed to identify breakthrough infections. Blood culture was offered to any child with a history of fever ≥3 days within the last 7 days. A total of 81 children received a second dose of TCV in November 2019 during a catch-up campaign organized by the Sindh government.
resultsNearly all participants seroconverted (802 of 837; 95.8%) at 4-6 weeks after vaccination. A total of 4 years after vaccination, 438 of 579 (75.6%) participants remained above the seroconversion threshold. The geometric mean titer (U/mL) of anti-Vi IgG at 4-6 weeks was 832.6 (95% confidence interval [CI]: 768.0-902.6); at 4 years after vaccination, the geometric mean titers in children aged 6 months to 2 years (12.6, [95% CI: 9.8-16.3]) and >2-5 years (40.1, [95% CI: 34.4-46.6]) were lower than in children aged >5-10 years (71.1, [95% CI: 59.5-85.0]). During 4 years of follow-up, nine children had culture-confirmed Salmonella Typhi infection; these infections occurred after a median duration of 3.4 years. All enteric fever cases seroconverted at 4-6 weeks after vaccination and seven (70.0%) remained seroconverted 4 years after vaccination.
conclusionsWe observed 95.8% seroconversion after a single dose of TCV. There was a decay in anti-Vi IgG titers, and, at 4 years, approximately 75.6% remained seroconverted. There was a faster decay in children aged ≤2 years. Breakthrough infections were documented after a median 3.4 years after vaccination.
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