Browsing by Author "Azman AS"

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    Alternative observational designs to estimate the effectiveness of one dose of oral cholera vaccine in Lusaka, Zambia.
    (2020-Mar-13) Ferreras E; Blake A; Chewe O; Mwaba J; Zulu G; Poncin M; Rakesh A; Page AL; Quilici ML; Azman AS; Cohuet S; Ciglenecki I; Malama K; Chizema-Kawesha E; Luquero FJ; Médecins Sans Frontières, Geneva, Switzerland.; Department of Pathology and Microbiology, University Teaching Hospital, Lusaka, Zambia.; Institut Pasteur, Paris, France.; Centre for Infectious Diseases Research in Zambia, Lusaka, Zambia.; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.; Zambia National Public Health Institute, Lusaka, Zambia.; Epicentre, Paris, France.; Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.; Ministry of Health, Lusaka, Zambia.; CIDRZ; Centre for Infectious Disease Research in Zambia (CIDRZ)
    We conducted a matched case-control (MCC), test-negative case-control (TNCC) and case-cohort study in 2016 in Lusaka, Zambia, following a mass vaccination campaign. Confirmed cholera cases served as cases in all three study designs. In the TNCC, control-subjects were cases with negative cholera culture and polymerase chain reaction results. Matched controls by age and sex were selected among neighbours of the confirmed cases in the MCC study. For the case-cohort study, we recruited a cohort of randomly selected individuals living in areas considered at-risk of cholera. We recruited 211 suspected cases (66 confirmed cholera cases and 145 non-cholera diarrhoea cases), 1055 matched controls and a cohort of 921. Adjusted vaccine effectiveness of one dose of oral cholera vaccine (OCV) was 88.9% (95% confidence interval (CI) 42.7-97.8) in the MCC study, 80.2% (95% CI: 16.9-95.3) in the TNCC design and 89.4% (95% CI: 64.6-96.9) in the case-cohort study. Three study designs confirmed the short-term effectiveness of single dose OCV. Major healthcare-seeking behaviour bias did not appear to affect our estimates. Most of the protection among vaccinated individuals could be attributed to the direct effect of the vaccine.
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    Estimating the proportion of clinically suspected cholera cases that are true Vibrio cholerae infections: A systematic review and meta-analysis.
    (2023-Sep) Wiens KE; Xu H; Zou K; Mwaba J; Lessler J; Malembaka EB; Demby MN; Bwire G; Qadri F; Lee EC; Azman AS; Division of Tropical and Humanitarian Medicine, Geneva University Hospitals, Geneva, Switzerland.; Department of Pathology and Microbiology, University Teaching Hospital, Lusaka, Zambia.; Geneva Centre for Emerging Viral Diseases, Geneva University Hospitals, Geneva, Switzerland.; Department of Biomedical Sciences, School of Health Sciences, University of Zambia, Lusaka, Zambia.; Infectious Diseases Division, International Centre for Diarrhoeal Disease Research Bangladesh (icddr,b), Dhaka, Bangladesh.; Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America.; Carolina Population Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.; Center for Tropical Diseases and Global Health (CTDGH), Université Catholique de Bukavu, Bukavu, Democratic Republic of the Congo.; Division of Public Health Emergency Preparedness and Response, Ministry of Health, Kampala, Uganda.; Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.; Centre for Infectious Disease Research in Zambia (CIDRZ), Lusaka, Zambia.; Department of Epidemiology and Biostatistics, College of Public Health, Temple University, Philadelphia, Pennsylvania, United States of America.
    BACKGROUND: Cholera surveillance relies on clinical diagnosis of acute watery diarrhea. Suspected cholera case definitions have high sensitivity but low specificity, challenging our ability to characterize cholera burden and epidemiology. Our objective was to estimate the proportion of clinically suspected cholera that are true Vibrio cholerae infections and identify factors that explain variation in positivity. METHODS AND FINDINGS: We conducted a systematic review of studies that tested ≥10 suspected cholera cases for V. cholerae O1/O139 using culture, PCR, and/or a rapid diagnostic test. We searched PubMed, Embase, Scopus, and Google Scholar for studies that sampled at least one suspected case between January 1, 2000 and April 19, 2023, to reflect contemporary patterns in V. cholerae positivity. We estimated diagnostic test sensitivity and specificity using a latent class meta-analysis. We estimated V. cholerae positivity using a random-effects meta-analysis, adjusting for test performance. We included 119 studies from 30 countries. V. cholerae positivity was lower in studies with representative sampling and in studies that set minimum ages in suspected case definitions. After adjusting for test performance, on average, 52% (95% credible interval (CrI): 24%, 80%) of suspected cases represented true V. cholerae infections. After adjusting for test performance and study methodology, the odds of a suspected case having a true infection were 5.71 (odds ratio 95% CrI: 1.53, 15.43) times higher when surveillance was initiated in response to an outbreak than in non-outbreak settings. Variation across studies was high, and a limitation of our approach was that we were unable to explain all the heterogeneity with study-level attributes, including diagnostic test used, setting, and case definitions. CONCLUSIONS: In this study, we found that burden estimates based on suspected cases alone may overestimate the incidence of medically attended cholera by 2-fold. However, accounting for cases missed by traditional clinical surveillance is key to unbiased cholera burden estimates. Given the substantial variability in positivity between settings, extrapolations from suspected to confirmed cases, which is necessary to estimate cholera incidence rates without exhaustive testing, should be based on local data.