Last data update: May 13, 2024. (Total: 46773 publications since 2009)
Records 1-4 (of 4 Records) |
Query Trace: Fasano N[original query] |
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Estimating typhoid incidence from community-based serosurveys: A multicohort study in Bangladesh, Nepal, Pakistan and Ghana (preprint)
Aiemjoy K , Seidman JC , Saha S , Munira SJ , Islam Sajib MS , Sium SMA , Sarkar A , Alam N , Zahan FN , Kabir MS , Tamrakar D , Vaidya K , Shrestha R , Shakya J , Katuwal N , Shrestha S , Yousafzai MT , Iqbal J , Dehraj IF , Ladak Y , Maria N , Adnan M , Pervaiz S , Carter AS , Longley AT , Fraser C , Ryan ET , Nodoushani A , Fasano A , Leonard MM , Kenyon V , Bogoch II , Jeon HJ , Haselbeck A , Park SE , Zellweger RM , Marks F , Owusu-Dabo E , Adu-Sarkodie Y , Owusu M , Teunis P , Luby SP , Garrett DO , Qamar FN , Saha SK , Charles RC , Andrews JR . medRxiv 2022 2021.10.20.21265277 Background The incidence of enteric fever, an invasive bacterial infection caused by typhoidal Salmonellae, is largely unknown in regions lacking blood culture surveillance. New serologic markers have proven accurate in diagnosing enteric fever, but whether they could be used to reliably estimate population-level incidence is unknown.Methods We collected longitudinal blood samples from blood culture-confirmed enteric fever cases enrolled from surveillance studies in Bangladesh, Nepal, Pakistan, and Ghana and conducted cross-sectional serosurveys in the catchment areas of each surveillance site. We used ELISAs to measure quantitative IgA and IgG antibody responses to Hemolysin E (HlyE) and S. Typhi lipopolysaccharide (LPS). We used Bayesian hierarchical models to fit two-phase power-function decay models to the longitudinal antibody responses among enteric fever cases and used the joint distributions of the peak antibody titers and decay rate to estimate population-level incidence rates from cross-sectional serosurveys.Findings The longitudinal antibody kinetics for all antigen-isotypes were similar across countries and did not vary by clinical severity. The seroincidence of typhoidal Salmonella infection among children <5 years ranged between 58.5 per 100 person-years (95% CI: 42.1 - 81.4) in Dhaka, Bangladesh to 6.6 (95% CI: 4.3-9.9) in Kavrepalanchok, Nepal, and followed the same rank order as clinical incidence estimates.Interpretation The approach described here has the potential to expand the geographic scope of typhoidal Salmonella surveillance and generate incidence estimates that are comparable across geographic regions and time.Funding This work was supported by the Bill and Melinda Gates Foundation (INV-000572).Evidence before this study Previous studies have identified serologic responses to two antigens (Hemolysin E [HlyE] and Salmonella lipopolysaccharide [LPS]) as promising diagnostic markers of acute typhoidal Salmonella infection. We reviewed the evidence for seroepidemiology tools for enteric fever available as of November 01, 2021, by searching the National Library of Medicine article database and medRxiv for preprint publications, published in English, using the terms “enteric fever”, “typhoid fever”, “Salmonella Typhi”, “Salmonella Paratyphi”, “typhoidal Salmonella”, “Hemolysin E”, “Salmonella lipopolysaccharide”, “seroconversion”, “serosurveillance”, “seroepidemiology”, “seroprevalence” and “seropositivity.” We found no studies using HlyE or LPS as markers to measure the incidence or prevalence of enteric fever in a population. Anti-Vi IgG responses were used as a marker of population seroprevalence in cross-sectional studies conducted in South Africa, Fiji, and Nepal, but were not used to calculate population-based incidence estimates.Added value of this study We developed and validated a method to estimate typhoidal Salmonella incidence in cross-sectional population samples using antibody responses measured from dried blood spots. First, using longitudinal dried blood spots collected from over 1400 blood culture-confirmed cases in four countries, we modeled the longitudinal dynamics of antibody responses for up to two years following infection, accounting for heterogeneity in antibody responses and age-dependence. We found that longitudinal antibody responses were highly consistent across four countries on two continents and did not differ by clinical severity. We then used these antibody kinetic parameters to estimate incidence in population-based samples in six communities across the four countries, where concomitant population-based incidence was measured using blood cultures. Seroincidence estimates were much higher than blood-culture-based case estimates across all six sites, suggestive of a high incidence of asymptomatic or unrecognized infections. Still, the rank order of seroincidence and culture-based incidence rates were the same, with the highest rates in Bangladesh and lowest in Ghana.Implications of all the available evidence Many a -risk low- and middle-income countries lack data on typhoid incidence needed to inform and evaluate vaccine introduction. Even in countries where incidence estimates are available, data are typically geographically and temporally sparse due to the resources necessary to initiate and sustain blood culture surveillance. We found that typhoidal Salmonella infection incidence can be estimated from community-based serosurveys using dried blood spots, representing an efficient and scalable approach for generating the typhoid burden data needed to inform typhoid control programs in resource-constrained settings.Competing Interest StatementThe authors have declared no competing interest.Funding StatementThis study was funded by th eBill and Melinda Gates Foundation (grant INV-000572)Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:Institutional Review Boards in the United States (Centers for Disease Control and Prevention; Stanford University Institutional Review Board), Bangladesh (Bangladesh Institute of Child Health Ethical Review Committee), Nepal (Nepal Health Research Council Ethical Review Board), Pakistan (AKU Ethic Review Committee and Pakistan National Bioethics Committee), Korea (International Vaccine Institute IRB), Belgium (Institute of Tropical Medicine Antwerp Institutional Review Board) and Ghana (Komfo Anokye Teaching Hospital, Committee on Human Research, Publication and Ethics) approved the study forms and protocols.I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).YesI have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.YesAll data produced in the present study are available upon reasonable request to the authors |
Estimating typhoid incidence from community-based serosurveys: a multicohort study
Aiemjoy K , Seidman JC , Saha S , Munira SJ , Islam Sajib MS , Sium SMA , Sarkar A , Alam N , Zahan FN , Kabir MS , Tamrakar D , Vaidya K , Shrestha R , Shakya J , Katuwal N , Shrestha S , Yousafzai MT , Iqbal J , Dehraj IF , Ladak Y , Maria N , Adnan M , Pervaiz S , Carter AS , Longley AT , Fraser C , Ryan ET , Nodoushani A , Fasano A , Leonard MM , Kenyon V , Bogoch II , Jeon HJ , Haselbeck A , Park SE , Zellweger RM , Marks F , Owusu-Dabo E , Adu-Sarkodie Y , Owusu M , Teunis P , Luby SP , Garrett DO , Qamar FN , Saha SK , Charles RC , Andrews JR . Lancet Microbe 2022 3 (8) e578-e587 BACKGROUND: The incidence of enteric fever, an invasive bacterial infection caused by typhoidal Salmonellae (Salmonella enterica serovars Typhi and Paratyphi), is largely unknown in regions without blood culture surveillance. The aim of this study was to evaluate whether new diagnostic serological markers for typhoidal Salmonella can reliably estimate population-level incidence. METHODS: We collected longitudinal blood samples from patients with blood culture-confirmed enteric fever enrolled from surveillance studies in Bangladesh, Nepal, Pakistan, and Ghana between 2016 and 2021 and conducted cross-sectional serosurveys in the catchment areas of each surveillance site. We used ELISAs to measure quantitative IgA and IgG antibody responses to hemolysin E and S Typhi lipopolysaccharide. We used Bayesian hierarchical models to fit two-phase power-function decay models to the longitudinal antibody responses among enteric fever cases and used the joint distributions of the peak antibody titres and decay rate to estimate population-level incidence rates from cross-sectional serosurveys. FINDINGS: The longitudinal antibody kinetics for all antigen-isotypes were similar across countries and did not vary by clinical severity. The seroincidence of typhoidal Salmonella infection among children younger than 5 years ranged between 58·5 per 100 person-years (95% CI 42·1-81·4) in Dhaka, Bangladesh, to 6·6 per 100 person-years (4·3-9·9) in Kavrepalanchok, Nepal, and followed the same rank order as clinical incidence estimates. INTERPRETATION: The approach described here has the potential to expand the geographical scope of typhoidal Salmonella surveillance and generate incidence estimates that are comparable across geographical regions and time. FUNDING: Bill & Melinda Gates Foundation. TRANSLATIONS: For the Nepali, Bengali and Urdu translations of the abstract see Supplementary Materials section. |
Qualitative analysis of immunization programs with most improved childhood vaccination coverage from 2001 to 2004
Groom H , Kennedy A , Evans V , Fasano N . J Public Health Manag Pract 2010 16 (1) E1-E8 State and urban immunization programs are responsible for the implementation of comprehensive programs to vaccinate populations within their geographic area. Given the variability in immunization coverage rates between geographic areas, the purpose of this two-phase study was to first identify the state and urban areas that achieved the highest increases in coverage, and then those with the highest sustained coverage, between two designated periods, and to interview key program staff members and their community counterparts to capture their perspectives on what factors may have contributed to increasing and sustaining high rates. In this article, we describe phase 1, in which we visited the seven sites that achieved the largest increases in coverage from 2001 to 2004. Results describe outcomes from the 71 semistructured key informant interviews with internal staff and external partners at the site's immunization programs. Interview transcripts were analyzed qualitatively, using a general inductive approach. Common challenges encountered among the seven sites included increasing reluctance among parents and overcoming barriers to accessing care. Common strategies to address these and other challenges included collecting and using data on immunization coverage, developing communication and education efforts, and continuously reaching out and collaborating with immunization partners. Lessons learned from these programs may help inform others who are working to improve childhood immunization delivery and coverage in their own programs. |
A qualitative analysis of immunization programs with sustained high coverage, 2000-2005
Kennedy A , Groom H , Evans V , Fasano N . J Public Health Manag Pract 2010 16 (1) E9-E17 Despite record-high immunization coverage nationally, there is considerable variation across state and local immunization programs, which are responsible for the implementation of vaccine recommendations in their jurisdictions. The objectives of this study were to describe activities of state and local immunization programs that sustained high coverage levels across several years and to identify common themes and practical examples for sustaining childhood vaccination coverage rates that could be applied elsewhere. We conducted 95 semi-structured key informant interviews with internal staff members and external partners at the 10 immunization programs with the highest sustained childhood immunization coverage from 2000 to 2005, as measured by the National Immunization Survey. Interview transcripts were analyzed qualitatively using a general inductive approach. Common themes across the 10 programs included maintaining a strong program infrastructure, using available data to drive planning and decision making, a commitment to building and sustaining relationships, and a focus on education and communication. Given the challenges of an increasingly complex immunization system, the lessons learned from these programs may help inform others who are working to improve childhood immunization delivery and coverage in their own programs. |
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