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Hammitt LL, Etyang AO, Morpeth SC, Ojal J, Mutuku A, Mturi N, Moisi JC, Adetifa IM, Karani A, Akech DO, Otiende M, Bwanaali T, Wafula J, Mataza C, Mumbo E, Tabu C, Knoll MD, Bauni E, Marsh K, Williams TN, Kamau T, Sharif SK, Levine OS, Scott JAG. Effect of ten-valent pneumococcal conjugate vaccine on invasive pneumococcal disease and nasopharyngeal carriage in Kenya: a longitudinal surveillance study. Lancet 2019; 393:2146-2154. [PMID: 31000194 PMCID: PMC6548991 DOI: 10.1016/s0140-6736(18)33005-8] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 10/19/2018] [Accepted: 11/15/2018] [Indexed: 01/20/2023]
Abstract
BACKGROUND Ten-valent pneumococcal conjugate vaccine (PCV10), delivered at 6, 10, and 14 weeks of age was introduced in Kenya in January, 2011, accompanied by a catch-up campaign in Kilifi County for children aged younger than 5 years. Coverage with at least two PCV10 doses in children aged 2-11 months was 80% in 2011 and 84% in 2016; coverage with at least one dose in children aged 12-59 months was 66% in 2011 and 87% in 2016. We aimed to assess PCV10 effect against nasopharyngeal carriage and invasive pneumococcal disease (IPD) in children and adults in Kilifi County. METHODS This study was done at the KEMRI-Wellcome Trust Research Programme among residents of the Kilifi Health and Demographic Surveillance System, a rural community on the Kenyan coast covering an area of 891 km2. We linked clinical and microbiological surveillance for IPD among admissions of all ages at Kilifi County Hospital, Kenya, which serves the community, to the Kilifi Health and Demographic Surveillance System from 1999 to 2016. We calculated the incidence rate ratio (IRR) comparing the prevaccine (Jan 1, 1999-Dec 31, 2010) and postvaccine (Jan 1, 2012-Dec 31, 2016) eras, adjusted for confounding, and reported percentage reduction in IPD as 1 minus IRR. Annual cross-sectional surveys of nasopharyngeal carriage were done from 2009 to 2016. FINDINGS Surveillance identified 667 cases of IPD in 3 211 403 person-years of observation. Yearly IPD incidence in children younger than 5 years reduced sharply in 2011 following vaccine introduction and remained low (PCV10-type IPD: 60·8 cases per 100 000 in the prevaccine era vs 3·2 per 100 000 in the postvaccine era [adjusted IRR 0·08, 95% CI 0·03-0·22]; IPD caused by any serotype: 81·6 per 100 000 vs 15·3 per 100 000 [0·32, 0·17-0·60]). PCV10-type IPD also declined in the post-vaccination era in unvaccinated age groups (<2 months [no cases in the postvaccine era], 5-14 years [adjusted IRR 0·26, 95% CI 0·11-0·59], and ≥15 years [0·19, 0·07-0·51]). Incidence of non-PCV10-type IPD did not differ between eras. In children younger than 5 years, PCV10-type carriage declined between eras (age-standardised adjusted prevalence ratio 0·26, 95% CI 0·19-0·35) and non-PCV10-type carriage increased (1·71, 1·47-1·99). INTERPRETATION Introduction of PCV10 in Kenya, accompanied by a catch-up campaign, resulted in a substantial reduction in PCV10-type IPD in children and adults without significant replacement disease. Although the catch-up campaign is likely to have brought forward the benefits by several years, the study suggests that routine infant PCV10 immunisation programmes will provide substantial direct and indirect protection in low-income settings in tropical Africa. FUNDING Gavi, The Vaccine Alliance and The Wellcome Trust of Great Britain.
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Affiliation(s)
- Laura L Hammitt
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
| | - Anthony O Etyang
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Susan C Morpeth
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - John Ojal
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Alex Mutuku
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | - Neema Mturi
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | - Jennifer C Moisi
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK; Pfizer Vaccines, Paris, France
| | - Ifedayo M Adetifa
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Angela Karani
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | - Donald O Akech
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | - Mark Otiende
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | - Tahreni Bwanaali
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Jackline Wafula
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | | | | | - Collins Tabu
- National Vaccines and Immunization Programme, Ministry of Health, Kenya
| | - Maria Deloria Knoll
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Evasius Bauni
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | - Kevin Marsh
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Thomas N Williams
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Imperial College, London, UK; INDEPTH Network, Accra, Ghana
| | - Tatu Kamau
- National Vaccines and Immunization Programme, Ministry of Health, Kenya
| | - Shahnaaz K Sharif
- National Vaccines and Immunization Programme, Ministry of Health, Kenya
| | - Orin S Levine
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; Bill & Melinda Gates Foundation, Seattle, WA, USA
| | - J Anthony G Scott
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK; INDEPTH Network, Accra, Ghana
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Silaba M, Ooko M, Bottomley C, Sande J, Benamore R, Park K, Ignas J, Maitland K, Mturi N, Makumi A, Otiende M, Kagwanja S, Safari S, Ochola V, Bwanaali T, Bauni E, Gleeson F, Deloria Knoll M, Adetifa I, Marsh K, Williams TN, Kamau T, Sharif S, Levine OS, Hammitt LL, Scott JAG. Effect of 10-valent pneumococcal conjugate vaccine on the incidence of radiologically-confirmed pneumonia and clinically-defined pneumonia in Kenyan children: an interrupted time-series analysis. Lancet Glob Health 2019; 7:e337-e346. [PMID: 30784634 PMCID: PMC6379823 DOI: 10.1016/s2214-109x(18)30491-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 09/20/2018] [Accepted: 10/23/2018] [Indexed: 12/30/2022]
Abstract
BACKGROUND Pneumococcal conjugate vaccines (PCV) are highly protective against invasive pneumococcal disease caused by vaccine serotypes, but the burden of pneumococcal disease in low-income and middle-income countries is dominated by pneumonia, most of which is non-bacteraemic. We examined the effect of 10-valent PCV on the incidence of pneumonia in Kenya. METHODS We linked prospective hospital surveillance for clinically-defined WHO severe or very severe pneumonia at Kilifi County Hospital, Kenya, from 2002 to 2015, to population surveillance at Kilifi Health and Demographic Surveillance System, comprising 45 000 children younger than 5 years. Chest radiographs were read according to a WHO standard. A 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PCV10) was introduced in Kenya in January, 2011. In Kilifi, there was a three-dose catch-up campaign for infants (aged <1 year) and a two-dose catch-up campaign for children aged 1-4 years, between January and March, 2011. We estimated the effect of PCV10 on the incidence of clinically-defined and radiologically-confirmed pneumonia through interrupted time-series analysis, accounting for seasonal and temporal trends. FINDINGS Between May 1, 2002 and March 31, 2015, 44 771 children aged 2-143 months were admitted to Kilifi County Hospital. We excluded 810 admissions between January and March, 2011, and 182 admissions during nurses' strikes. In 2002-03, the incidence of admission with clinically-defined pneumonia was 2170 per 100 000 in children aged 2-59 months. By the end of the catch-up campaign in 2011, 4997 (61·1%) of 8181 children aged 2-11 months had received at least two doses of PCV10 and 23 298 (62·3%) of 37 416 children aged 12-59 months had received at least one dose. Across the 13 years of surveillance, the incidence of clinically-defined pneumonia declined by 0·5% per month, independent of vaccine introduction. There was no secular trend in the incidence of radiologically-confirmed pneumonia over 8 years of study. After adjustment for secular trend and season, incidence rate ratios for admission with radiologically-confirmed pneumonia, clinically-defined pneumonia, and diarrhoea (control condition), associated temporally with PCV10 introduction and the catch-up campaign, were 0·52 (95% CI 0·32-0·86), 0·73 (0·54-0·97), and 0·63 (0·31-1·26), respectively. Immediately before PCV10 was introduced, the annual incidence of clinically-defined pneumonia was 1220 per 100 000; this value was reduced by 329 per 100 000 at the point of PCV10 introduction. INTERPRETATION Over 13 years, admissions to Kilifi County Hospital for clinically-defined pneumonia decreased sharply (by 27%) in association with the introduction of PCV10, as did the incidence of radiologically-confirmed pneumonia (by 48%). The burden of hospital admissions for childhood pneumonia in Kilifi, Kenya, has been reduced substantially by the introduction of PCV10. FUNDING Gavi, The Vaccine Alliance and Wellcome Trust.
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Affiliation(s)
- Micah Silaba
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Michael Ooko
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Christian Bottomley
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Joyce Sande
- Aga Khan University Hospital, Nairobi, Kenya
| | - Rachel Benamore
- Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Kate Park
- Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - James Ignas
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Kathryn Maitland
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Imperial College, London, UK
| | - Neema Mturi
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Kilifi County Hospital, Kilifi, Kenya
| | - Anne Makumi
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Mark Otiende
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | | | - Victor Ochola
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Tahreni Bwanaali
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Evasius Bauni
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Oxford University, Oxford, UK
| | - Fergus Gleeson
- Oxford University Hospitals NHS Foundation Trust, Oxford, UK; Oxford University, Oxford, UK
| | - Maria Deloria Knoll
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, USA
| | - Ifedayo Adetifa
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Kevin Marsh
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Oxford University, Oxford, UK
| | - Thomas N Williams
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Imperial College, London, UK; INDEPTH Network, Accra, Ghana
| | | | | | - Orin S Levine
- The Bill & Melinda Gates Foundation, Seattle, WA, USA
| | - Laura L Hammitt
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, USA
| | - J Anthony G Scott
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK; Oxford University, Oxford, UK; INDEPTH Network, Accra, Ghana.
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Adetifa IMO, Karia B, Mutuku A, Bwanaali T, Makumi A, Wafula J, Chome M, Mwatsuma P, Bauni E, Hammitt LL, Mataza C, Tabu C, Kamau T, Williams TN, Scott JAG. Coverage and timeliness of vaccination and the validity of routine estimates: Insights from a vaccine registry in Kenya. Vaccine 2018; 36:7965-7974. [PMID: 30416017 PMCID: PMC6288063 DOI: 10.1016/j.vaccine.2018.11.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 10/31/2018] [Accepted: 11/01/2018] [Indexed: 11/02/2022]
Abstract
BACKGROUND The benefits of childhood vaccines are critically dependent on vaccination coverage. We used a vaccine registry (as gold standard) in Kenya to quantify errors in routine coverage methods (surveys and administrative reports), to estimate the magnitude of survivor bias, contrast coverage with timeliness and use both measures to estimate population immunity. METHODS Vaccination records of children in the Kilifi Health and Demographic Surveillance System (KHDSS), Kenya were combined with births, deaths, migration and residence data from 2010 to 17. Using inverse survival curves, we estimated up-to-date and age-appropriate vaccination coverage, calculated mean vaccination coverage in infancy as the area under the inverse survival curves, and estimated the proportion of fully immunised children (FIC). Results were compared with published coverage estimates. Risk factors for vaccination were assessed using Cox regression models. RESULTS We analysed data for 49,090 infants and 48,025 children aged 12-23 months in 6 birth cohorts and 6 cross-sectional surveys respectively, and found 2nd year of life surveys overestimated coverage by 2% compared to birth cohorts. Compared to mean coverage in infants, static coverage at 12 months was exaggerated by 7-8% for third doses of oral polio, pentavalent (Penta3) and pneumococcal conjugate vaccines, and by 24% for the measles vaccine. Surveys and administrative coverage also underestimated the proportion of the fully immunised child by 10-14%. For BCG, Penta3 and measles, timeliness was 23-44% higher in children born in a health facility but 20-37% lower in those who first attended during vaccine stock outs. CONCLUSIONS Standard coverage surveys in 12-23 month old children overestimate protection by ignoring timeliness, and survivor and recall biases. Where delayed vaccination is common, up-to-date coverage will give biased estimates of population immunity. Surveys and administrative methods also underestimate FIC prevalence. Better measurement of coverage and more sophisticated analyses are required to control vaccine preventable diseases.
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Affiliation(s)
- Ifedayo M O Adetifa
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya; Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, WC1E 7HT London, UK.
| | - Boniface Karia
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya.
| | - Alex Mutuku
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya
| | - Tahreni Bwanaali
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya
| | - Anne Makumi
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya
| | - Jackline Wafula
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya.
| | - Martina Chome
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya.
| | - Pauline Mwatsuma
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya
| | - Evasius Bauni
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya
| | - Laura L Hammitt
- Centre for International Health, Johns Hopkins University, Baltimore, MD, United States.
| | - Christine Mataza
- County Department of Health, Kilifi County Hospital, PO Box 491-80108, Kilifi, Kenya.
| | - Collins Tabu
- National Vaccines and Immunisations Programme, Ministry of Health, Kenya
| | - Tatu Kamau
- Vector Borne Diseases Control Unit, Ministry of Health, Kenya
| | - Thomas N Williams
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya; Department of Medicine, Imperial College, St Mary's Hospital, Praed Street, London, United Kingdom; INDEPTH Network, Accra, Ghana.
| | - J Anthony G Scott
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, PO Box 230-80108, Kilifi, Kenya; Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, WC1E 7HT London, UK; INDEPTH Network, Accra, Ghana.
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Adetifa IMO, Bwanaali T, Wafula J, Mutuku A, Karia B, Makumi A, Mwatsuma P, Bauni E, Hammitt LL, Nokes DJ, Maree E, Tabu C, Kamau T, Mataza C, Williams TN, Scott JAG. Cohort Profile: The Kilifi Vaccine Monitoring Study. Int J Epidemiol 2018; 46:792-792h. [PMID: 27789669 PMCID: PMC5654374 DOI: 10.1093/ije/dyw202] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/21/2016] [Indexed: 11/14/2022] Open
Affiliation(s)
- Ifedayo M O Adetifa
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.,Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - Tahreni Bwanaali
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.,Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - Jackline Wafula
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Alex Mutuku
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Boniface Karia
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Anne Makumi
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Pauline Mwatsuma
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Evasius Bauni
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Laura L Hammitt
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.,Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - D James Nokes
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.,School of Life Sciences and WIDER, University of Warwick, Coventry, UK
| | | | | | - Tatu Kamau
- Vector Borne Diseases Control Unit, Ministry of Health, Nairobi, Kenya
| | | | - Thomas N Williams
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.,Department of Medicine, Imperial College, St Mary's Hospital, London, UK.,INDEPTH Network, Accra, Ghana
| | - J Anthony G Scott
- Epidemiology and Demography Department, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.,Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.,INDEPTH Network, Accra, Ghana
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Ojal J, Flasche S, Hammitt LL, Akech D, Kiti MC, Kamau T, Adetifa I, Nurhonen M, Scott JAG, Auranen K. Sustained reduction in vaccine-type invasive pneumococcal disease despite waning effects of a catch-up campaign in Kilifi, Kenya: A mathematical model based on pre-vaccination data. Vaccine 2017; 35:4561-4568. [PMID: 28729018 PMCID: PMC5571446 DOI: 10.1016/j.vaccine.2017.07.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 07/04/2017] [Accepted: 07/05/2017] [Indexed: 01/22/2023]
Abstract
We predict a substantial decline in the carriage prevalence of vaccine serotypes. About a 56% reduction in invasive pneumococcal disease is also predicted. The decline is predicted to be sustainable ten years post-vaccination. The current vaccination schedule is unlikely to achieve elimination of vaccine serotypes.
Background In 2011, Kenya introduced the 10-valent pneumococcal conjugate vaccine together with a catch-up campaign for children aged <5 years in Kilifi County. In a post-vaccination surveillance study based in Kilifi, there was a substantial decline in invasive pneumococcal disease (IPD). However, given the continued circulation of the vaccine serotypes it is possible that vaccine-serotype disease may re-emerge once the effects of the catch-up campaign wear off. Methods We developed a compartmental, age-structured dynamic model of pneumococcal carriage and invasive disease for three serotype groups: the 10-valent vaccine serotypes and two groups of non-vaccine serotypes based on their susceptibility to mutual competition. The model was calibrated to age- and serotype-specific data on carriage and IPD in the pre-vaccination era and used to predict carriage prevalence and IPD up to ten years post-vaccination in Kilifi. The model was validated against the observed carriage prevalence after vaccine introduction. Results The model predicts a sustained reduction in vaccine-type pneumococcal carriage prevalence from 33% to 8% in infants and from 30% to 8% in 1–5 year olds over the 10-year period following vaccine introduction. The incidence of IPD is predicted to decline across all age groups resulting in an overall reduction of 56% in the population, corresponding to 10.4 cases per 100,000 per year. The vaccine-type IPD incidence is estimated to decline by 83% while non-vaccine-type IPD incidence is predicted to increase by 52%. The model's predictions of carriage prevalence agrees well with the observed data in the first five years post-vaccination. Conclusion We predict a sustained and substantial decline in IPD through PCV vaccination and that the current regimen is insufficient to fully eliminate vaccine-serotype circulation in the model. We show that the observed impact is likely to be sustained despite waning effects of the catch-up campaign.
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Affiliation(s)
- John Ojal
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.
| | - Stefan Flasche
- Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Laura L Hammitt
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Donald Akech
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | - Moses C Kiti
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | - Tatu Kamau
- Kenya Ministry of Health, Nairobi, Kenya
| | - Ifedayo Adetifa
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Markku Nurhonen
- Department of Public Health Solutions, National Institute for Health and Welfare (THL), Finland
| | - J Anthony G Scott
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Kari Auranen
- Department of Public Health Solutions, National Institute for Health and Welfare (THL), Finland; Department of Mathematics and Statistics, University of Turku, Finland
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Hammitt LL, Crane RJ, Karani A, Mutuku A, Morpeth SC, Burbidge P, Goldblatt D, Kamau T, Sharif S, Mturi N, Scott JAG. Effect of Haemophilus influenzae type b vaccination without a booster dose on invasive H influenzae type b disease, nasopharyngeal carriage, and population immunity in Kilifi, Kenya: a 15-year regional surveillance study. Lancet Glob Health 2016; 4:e185-94. [PMID: 26853149 PMCID: PMC4763163 DOI: 10.1016/s2214-109x(15)00316-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 11/18/2015] [Accepted: 12/07/2015] [Indexed: 10/25/2022]
Abstract
BACKGROUND Haemophilus influenzae type b (Hib) conjugate vaccine, delivered as a three-dose series without a booster, was introduced into the childhood vaccination programme in Kenya in 2001. The duration of protection and need for a booster dose are unknown. We aimed to assess vaccine effectiveness, the impact of the vaccine on nasopharyngeal carriage, and population immunity after introduction of conjugate Hib vaccine in infancy without a booster dose in Kenya. METHODS This study took place in the Kilifi Health and Demographic Surveillance System (KHDSS), an area of Kenya that has been monitored for vital events and migration every 4 months since 2000. We analysed sterile site cultures for H influenzae type b from children (aged ≤12 years) admitted to the Kilifi County Hospital (KCH) from Jan 1, 2000, through to Dec 31, 2014. We determined the prevalence of nasopharyngeal carriage by undertaking cross-sectional surveys in random samples of KHDSS residents (of all ages) once every year from 2009 to 2012, and measured Hib antibody concentrations in five cross-sectional samples of children (aged ≤12 years) within the KHDSS (in 1998, 2000, 2004-05, 2007, and 2009). We calculated incidence rate ratios between the prevaccine era (2000-01) and the routine-use era (2004-14) and defined vaccine effectiveness as 1 minus the incidence rate ratio, expressed as a percentage. FINDINGS 40,482 children younger than 13 years resident in KHDSS were admitted to KCH between 2000 and 2014, 38,206 (94%) of whom had their blood cultured. The incidence of invasive H influenzae type b disease in children younger than 5 years declined from 62·6 (95% CI 46·0-83·3) per 100,000 in 2000-01 to 4·5 (2·5-7·5) per 100,000 in 2004-14, giving a vaccine effectiveness of 93% (95% CI 87-96). In the final 5 years of observation (2010-14), only one case of invasive H influenzae type b disease was detected in a child younger than 5 years. Nasopharyngeal H influenzae type b carriage was detected in one (0·2%) of 623 children younger than 5 years between 2009 and 2012. In the 2009 serosurvey, 92 (79%; 95% CI 70-86) of 117 children aged 4-35 months had long-term protective antibody concentrations. INTERPRETATION In this region of Kenya, use of a three-dose primary series of Hib vaccine without a booster dose has resulted in a significant and sustained reduction in invasive H influenzae type b disease. The prevalence of nasopharyngeal carriage is low and the profile of Hib antibodies suggests that protection wanes only after the age at greatest risk of disease. Although continued surveillance is important to determine whether effective control persists, these findings suggest that a booster dose is not currently required in Kenya. FUNDING Gavi, the Vaccine Alliance, Wellcome Trust, European Society for Paediatric Infectious Diseases, and National Institute for Health Research.
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Affiliation(s)
- Laura L Hammitt
- Department of Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
| | - Rosie J Crane
- Department of Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Angela Karani
- Department of Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Alex Mutuku
- Department of Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Susan C Morpeth
- Department of Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Polly Burbidge
- Institute of Child Health, University College London, London, UK
| | - David Goldblatt
- Institute of Child Health, University College London, London, UK
| | - Tatu Kamau
- Kenya Ministry of Public Health and Sanitation, Kilifi, Kenya
| | - Shahnaaz Sharif
- Kenya Ministry of Public Health and Sanitation, Kilifi, Kenya
| | - Neema Mturi
- Department of Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - J Anthony G Scott
- Department of Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
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Burton DC, Bigogo GM, Audi AO, Williamson J, Munge K, Wafula J, Ouma D, Khagayi S, Mugoya I, Mburu J, Muema S, Bauni E, Bwanaali T, Feikin DR, Ochieng PM, Mogeni OD, Otieno GA, Olack B, Kamau T, Van Dyke MK, Chen R, Farrington P, Montgomery JM, Breiman RF, Scott JAG, Laserson KF. Risk of Injection-Site Abscess among Infants Receiving a Preservative-Free, Two-Dose Vial Formulation of Pneumococcal Conjugate Vaccine in Kenya. PLoS One 2015; 10:e0141896. [PMID: 26509274 PMCID: PMC4625023 DOI: 10.1371/journal.pone.0141896] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 10/14/2015] [Indexed: 01/01/2023] Open
Abstract
There is a theoretical risk of adverse events following immunization with a preservative-free, 2-dose vial formulation of 10-valent-pneumococcal conjugate vaccine (PCV10). We set out to measure this risk. Four population-based surveillance sites in Kenya (total annual birth cohort of 11,500 infants) were used to conduct a 2-year post-introduction vaccine safety study of PCV10. Injection-site abscesses occurring within 7 days following vaccine administration were clinically diagnosed in all study sites (passive facility-based surveillance) and, also, detected by caregiver-reported symptoms of swelling plus discharge in two sites (active household-based surveillance). Abscess risk was expressed as the number of abscesses per 100,000 injections and was compared for the second vs first vial dose of PCV10 and for PCV10 vs pentavalent vaccine (comparator). A total of 58,288 PCV10 injections were recorded, including 24,054 and 19,702 identified as first and second vial doses, respectively (14,532 unknown vial dose). The risk ratio for abscess following injection with the second (41 per 100,000) vs first (33 per 100,000) vial dose of PCV10 was 1.22 (95% confidence interval [CI] 0.37–4.06). The comparator vaccine was changed from a 2-dose to 10-dose presentation midway through the study. The matched odds ratios for abscess following PCV10 were 1.00 (95% CI 0.12–8.56) and 0.27 (95% CI 0.14–0.54) when compared to the 2-dose and 10-dose pentavalent vaccine presentations, respectively. In Kenya immunization with PCV10 was not associated with an increased risk of injection site abscess, providing confidence that the vaccine may be safely used in Africa. The relatively higher risk of abscess following the 10-dose presentation of pentavalent vaccine merits further study.
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Affiliation(s)
- Deron C. Burton
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
- * E-mail:
| | - Godfrey M. Bigogo
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
| | - Allan O. Audi
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
| | - John Williamson
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- Center for Global Health, CDC, Atlanta, Georgia, United States of America
| | - Kenneth Munge
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | - Dominic Ouma
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
| | - Sammy Khagayi
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
| | - Isaac Mugoya
- Division of Vaccines and Immunization, Ministry of Public Health and Sanitation, Nairobi, Kenya
| | - James Mburu
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Shadrack Muema
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
| | - Evasius Bauni
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | - Daniel R. Feikin
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
| | - Peter M. Ochieng
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
| | - Ondari D. Mogeni
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
| | - George A. Otieno
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
| | - Beatrice Olack
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
| | - Tatu Kamau
- Division of Vaccines and Immunization, Ministry of Public Health and Sanitation, Nairobi, Kenya
| | | | - Robert Chen
- National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, CDC, Atlanta, Georgia, United States of America
| | | | - Joel M. Montgomery
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
| | - Robert F. Breiman
- International Emerging Infections Program, Global Disease Detection Response Center, CDC, Kisumu and Nairobi, Kenya
- Center for Global Health, CDC, Atlanta, Georgia, United States of America
| | - J. Anthony G. Scott
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Kayla F. Laserson
- Kenya Medical Research Institute (KEMRI)/Centers for Disease Control and Prevention (CDC) Research and Public Health Collaboration, Kisumu and Nairobi, Kenya
- Center for Global Health, CDC, Atlanta, Georgia, United States of America
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Hammitt LL, Akech DO, Morpeth SC, Karani A, Kihuha N, Nyongesa S, Bwanaali T, Mumbo E, Kamau T, Sharif SK, Scott JAG. Population effect of 10-valent pneumococcal conjugate vaccine on nasopharyngeal carriage of Streptococcus pneumoniae and non-typeable Haemophilus influenzae in Kilifi, Kenya: findings from cross-sectional carriage studies. Lancet Glob Health 2014; 2:e397-405. [PMID: 25103393 PMCID: PMC5628631 DOI: 10.1016/s2214-109x(14)70224-4] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Background The effect of 7-valent pneumococcal conjugate vaccine
(PCV) in developed countries was enhanced by indirect protection of unvaccinated
individuals, mediated by reduced nasopharyngeal carriage of vaccine-serotype
pneumococci. The potential indirect protection of 10-valent PCV (PCV10) in a
developing country setting is unknown. We sought to estimate the effectiveness of
introduction of PCV10 in Kenya against carriage of vaccine serotypes and its effect
on other bacteria. Methods PCV10 was introduced into the infant vaccination programme
in Kenya in January, 2011, accompanied by a catch-up campaign in Kilifi County for
children aged younger than 5 years. We did annual cross-sectional carriage studies
among an age-stratified, random population sample in the 2 years before and 2 years
after PCV10 introduction. A nasopharyngeal rayon swab specimen was collected from
each participant and was processed in accordance with WHO recommendations. Prevalence
ratios of carriage before and after introduction of PCV10 were calculated by
log-binomial regression. Findings About 500 individuals were enrolled each year (total
n=2031). Among children younger than 5 years, the baseline (2009–10) carriage
prevalence was 34% for vaccine-serotype Streptococcus
pneumoniae, 41% for non-vaccine-serotype Streptococcus
pneumoniae, and 54% for non-typeable Haemophilus
influenzae. After PCV10 introduction (2011–12), these percentages were
13%, 57%, and 40%, respectively. Adjusted prevalence ratios were 0·36 (95% CI
0·26–0·51), 1·37 (1·13–1·65), and 0·62 (0·52–0·75), respectively. Among individuals
aged 5 years or older, the adjusted prevalence ratios for vaccine-serotype and
non-vaccine-serotype S pneumoniae carriage were 0·34 (95% CI
0·18–0·62) and 1·13 (0·92–1·38), respectively. There was no change in prevalence
ratio for Staphylococcus aureus (adjusted prevalence ratio for
those <5 years old 1·02, 95% CI 0·52–1·99, and for those ≥5 years old 0·90,
0·60–1·35). Interpretation After programmatic use of PCV10 in Kilifi, carriage of
vaccine serotypes was reduced by two-thirds both in children younger than 5 years and
in older individuals. These findings suggest that PCV10 introduction in Africa will
have substantial indirect effects on invasive pneumococcal disease. Funding GAVI Alliance and Wellcome Trust.
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Affiliation(s)
- Laura L Hammitt
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
| | - Donald O Akech
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Susan C Morpeth
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Angela Karani
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Norbert Kihuha
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Sammy Nyongesa
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Tahreni Bwanaali
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | | | - Tatu Kamau
- Kenya Ministry of Health, Nairobi, Kenya
| | | | - J Anthony G Scott
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK; London School of Hygiene & Tropical Medicine, London, UK
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Hassan J, Gachara G, Mbugua F, Muchiri J, Symekhah S, Nakitari G, Borus P, Kamau T, Kombich J. Potency status of oral polio virus vaccine among retrieved field samples in Kenya. Int J Infect Dis 2014. [DOI: 10.1016/j.ijid.2014.03.1330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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10
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Ayieko P, Griffiths UK, Ndiritu M, Moisi J, Mugoya IK, Kamau T, English M, Scott JAG. Assessment of health benefits and cost-effectiveness of 10-valent and 13-valent pneumococcal conjugate vaccination in Kenyan children. PLoS One 2013; 8:e67324. [PMID: 23826268 PMCID: PMC3691111 DOI: 10.1371/journal.pone.0067324] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 05/20/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The GAVI Alliance supported 10-valent pneumococcal conjugate vaccine (PCV10) introduction in Kenya. We estimated the cost-effectiveness of introducing either PCV10 or the 13-valent vaccine (PCV13) from a societal perspective and explored the incremental impact of including indirect vaccine effects. METHODS The costs and effects of pneumococcal vaccination among infants born in Kenya in 2010 were assessed using a decision analytic model comparing PCV10 or PCV13, in turn, with no vaccination. Direct vaccine effects were estimated as a reduction in the incidence of pneumococcal meningitis, sepsis, bacteraemic pneumonia and non-bacteraemic pneumonia. Pneumococcal disease incidence was extrapolated from a population-based hospital surveillance system in Kilifi and adjustments were made for variable access to care across Kenya. We used vaccine efficacy estimates from a trial in The Gambia and accounted for serotype distribution in Kilifi. We estimated indirect vaccine protection and serotype replacement by extrapolating from the USA. Multivariable sensitivity analysis was conducted using Monte Carlo simulation. We assumed a vaccine price of US$ 3.50 per dose. FINDINGS The annual cost of delivering PCV10 was approximately US$14 million. We projected a 42.7% reduction in pneumococcal disease episodes leading to a US$1.97 million reduction in treatment costs and a 6.1% reduction in childhood mortality annually. In the base case analysis, costs per discounted DALY and per death averted by PCV10, amounted to US$ 59 (95% CI 26-103) and US$ 1,958 (95% CI 866-3,425), respectively. PCV13 introduction improved the cost-effectiveness ratios by approximately 20% and inclusion of indirect effects improved cost-effectiveness ratios by 43-56%. The break-even prices for introduction of PCV10 and PCV13 are US$ 0.41 and 0.51, respectively. CONCLUSIONS Introducing either PCV10 or PCV13 in Kenya is highly cost-effective from a societal perspective. Indirect effects, if they occur, would significantly improve the cost-effectiveness.
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Affiliation(s)
- Philip Ayieko
- Kenya Medical Research Institute/Wellcome Trust Programme, Nairobi, Kenya.
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van Hoek AJ, Ngama M, Ismail A, Chuma J, Cheburet S, Mutonga D, Kamau T, Nokes DJ. A cost effectiveness and capacity analysis for the introduction of universal rotavirus vaccination in Kenya: comparison between Rotarix and RotaTeq vaccines. PLoS One 2012; 7:e47511. [PMID: 23115650 PMCID: PMC3480384 DOI: 10.1371/journal.pone.0047511] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 09/12/2012] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Diarrhoea is an important cause of death in the developing world, and rotavirus is the single most important cause of diarrhoea associated mortality. Two vaccines (Rotarix and RotaTeq) are available to prevent rotavirus disease. This analysis was undertaken to aid the decision in Kenya as to which vaccine to choose when introducing rotavirus vaccination. METHODS Cost-effectiveness modelling, using national and sentinel surveillance data, and an impact assessment on the cold chain. RESULTS The median estimated incidence of rotavirus disease in Kenya was 3015 outpatient visits, 279 hospitalisations and 65 deaths per 100,000 children under five years of age per year. Cumulated over the first five years of life vaccination was predicted to prevent 34% of the outpatient visits, 31% of the hospitalizations and 42% of the deaths. The estimated prevented costs accumulated over five years totalled US$1,782,761 (direct and indirect costs) with an associated 48,585 DALYs. From a societal perspective Rotarix had a cost-effectiveness ratio of US$142 per DALY (US$5 for the full course of two doses) and RotaTeq US$288 per DALY ($10.5 for the full course of three doses). RotaTeq will have a bigger impact on the cold chain compared to Rotarix. CONCLUSION Vaccination against rotavirus disease is cost-effective for Kenya irrespective of the vaccine. Of the two vaccines Rotarix was the preferred choice due to a better cost-effectiveness ratio, the presence of a vaccine vial monitor, the requirement of fewer doses and less storage space, and proven thermo-stability.
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Affiliation(s)
- Albert Jan van Hoek
- Immunisation, Hepatitis and Blood Safety Department, Health Protection Agency, London, United Kingdom
| | - Mwanajuma Ngama
- Kenya Medical Research Institute, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
- * E-mail:
| | - Amina Ismail
- Division of Disease Surveillance and Response, Ministry of Public Health and Sanitation, Nairobi, Kenya
| | - Jane Chuma
- Kenya Medical Research Institute, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Samuel Cheburet
- Health Information System, Ministry of Health, Nairobi, Kenya
| | - David Mutonga
- Division of Disease Surveillance and Response, Ministry of Public Health and Sanitation, Nairobi, Kenya
| | - Tatu Kamau
- Division of Vaccines & Immunization, Ministry of Public Health and Sanitation, Nairobi, Kenya
| | - D. James Nokes
- Kenya Medical Research Institute, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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Abstract
OBJECTIVES To determine the current status of immunisation coverage in Western Kenya before intervention, to identify strengths and weaknesses of the existing programme in order to design educational interventions that could improve the services provided and find out the training needs of the mid-level managers of Kenya Expanded Programme of Immunisation. DESIGN Cross-sectional descriptive study. SETTING All thirty nine districts in Rift Valley, Western and Nyanza provinces. SUBJECTS Mid-level managers of Kenya Expanded Programme on Immunisation in the 39 districts and the provinces. These included Provincial Logisticians, Provincial Medical Officers of Health, District Medical Officers of Health, District Public Health Nurses, District Records and Health Information Officers, District Disease Surveillance Officers, and District Public Health Officers. MAIN OUTCOME MEASURES Number of staff trained on EPI, coverage rates and perceived training needs of the mid-level managers. RESULTS A total of eighty eight mid-level managers participated in the interviews. Most of these were District Public Health Nurses (40.9%) and District Health Information and Records Officers (23.9%). Only 49 (25%) of the District Health Management Team members had undergone training at the supervisory level. Eighteen districts (43.6%) had no member of the District Health Management Team that had ever been trained at the supervisory level. Using rates of Pentavalent 1 and measles coverage, Nyanza Province had the highest immunisation dropout rate (Pentavalent 1--measles) whereas Rift Valley Province had the lowest. The annual cumulative coverage for all the provinces by antigen was 80% for Pentavalent 1 and 2 and 60% for measles. The most requested need for inclusion in the training curriculum was maintenance of the cold chain equipment. CONCLUSIONS Most of the members in the study area have not been trained on Expanded Programme on Immunisation and may be ill-equipped to manage the complicated programmes needed to maximise delivery of services. The immunisation coverage in this area is low while the dropout rates are high. We therefore recommend that all the mid-level managers of Expanded Programme on Immunisation in this area be trained comprehensively through the Merck Vaccine Network--Africa programme using the World Health Organisation approved mid-level managers course.
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Affiliation(s)
- S O Ayaya
- Department of Child Health and Paediatrics, Faculty of Health Sciences, Moi University, Eldoret, Kenya
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Cowgill KD, Ndiritu M, Nyiro J, Slack MPE, Chiphatsi S, Ismail A, Kamau T, Mwangi I, English M, Newton CRJC, Feikin DR, Scott JAG. Effectiveness of Haemophilus influenzae type b Conjugate vaccine introduction into routine childhood immunization in Kenya. JAMA 2006; 296:671-8. [PMID: 16896110 PMCID: PMC1592684 DOI: 10.1001/jama.296.6.671] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
CONTEXT Haemophilus influenzae type b (Hib) conjugate vaccine is not perceived as a public health priority in Africa because data on Hib disease burden and vaccine effectiveness are scarce. Hib immunization was introduced in Kenyan infants in 2001. OBJECTIVE To define invasive Hib disease incidence and Hib vaccine program effectiveness in Kenya. DESIGN, SETTING, AND PATIENTS Culture-based surveillance for invasive Hib disease at Kilifi District Hospital from 2000 through 2005 was linked to demographic surveillance of 38,000 children younger than 5 years in Kilifi District, Kenya. Human immunodeficiency virus (HIV) infection and Hib vaccination status were determined for children with Hib disease admitted 2002-2005. INTERVENTIONS Introduction of conjugate Hib vaccine within the routine childhood immunization program at ages 6, 10, and 14 weeks beginning November 2001. MAIN OUTCOME MEASURES Incidence of culture-proven Hib invasive disease before and after vaccine introduction and vaccine program effectiveness. RESULTS Prior to vaccine introduction, the median age of children with Hib was 8 months; case fatality was 23%. Among children younger than 5 years, the annual incidence of invasive Hib disease 1 year before and 1 and 3 years after vaccine introduction was 66, 47, and 7.6 per 100,000, respectively. For children younger than 2 years, incidence was 119, 82, and 16 per 100,000, respectively. In 2004-2005, vaccine effectiveness was 88% (95% confidence interval, 73%-96%) among children younger than 5 years and 87% (95% confidence interval, 66%-96%) among children younger than 2 years. Of 53 children with Hib admitted during 2002-2005, 29 (55%) were age-ineligible to have received vaccine, 12 (23%) had not been vaccinated despite being eligible, and 12 (23%) had received 2 or more doses of vaccine (2 were HIV positive). CONCLUSIONS In Kenya, introduction of Hib vaccine into the routine childhood immunization program reduced Hib disease incidence among children younger than 5 years to 12% of its baseline level. This impact was not observed until the third year after vaccine introduction.
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Affiliation(s)
- Karen D Cowgill
- Epidemic Intelligence Service, Epidemiology Program Office, Division of Applied Public Health Training, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Ga, USA
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Ndiritu M, Cowgill KD, Ismail A, Chiphatsi S, Kamau T, Fegan G, Feikin DR, Newton CRJC, Scott JAG. Immunization coverage and risk factors for failure to immunize within the Expanded Programme on Immunization in Kenya after introduction of new Haemophilus influenzae type b and hepatitis b virus antigens. BMC Public Health 2006; 6:132. [PMID: 16707013 PMCID: PMC1475578 DOI: 10.1186/1471-2458-6-132] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Accepted: 05/17/2006] [Indexed: 01/07/2023] Open
Abstract
Background Kenya introduced a pentavalent vaccine including the DTP, Haemophilus influenzae type b and hepatitis b virus antigens in Nov 2001 and strengthened immunization services. We estimated immunization coverage before and after introduction, timeliness of vaccination and risk factors for failure to immunize in Kilifi district, Kenya. Methods In Nov 2002 we performed WHO cluster-sample surveys of >200 children scheduled for vaccination before or after introduction of pentavalent vaccine. In Mar 2004 we conducted a simple random sample (SRS) survey of 204 children aged 9–23 months. Coverage was estimated by inverse Kaplan-Meier survival analysis of vaccine-card and mothers' recall data and corroborated by reviewing administrative records from national and provincial vaccine stores. The contribution to timely immunization of distance from clinic, seasonal rainfall, mother's age, and family size was estimated by a proportional hazards model. Results Immunization coverage for three DTP and pentavalent doses was 100% before and 91% after pentavalent vaccine introduction, respectively. By SRS survey, coverage was 88% for three pentavalent doses. The median age at first, second and third vaccine dose was 8, 13 and 18 weeks. Vials dispatched to Kilifi District during 2001–2003 would provide three immunizations for 92% of the birth cohort. Immunization rate ratios were reduced with every kilometre of distance from home to vaccine clinic (HR 0.95, CI 0.91–1.00), rainy seasons (HR 0.73, 95% CI 0.61–0.89) and family size, increasing progressively up to 4 children (HR 0.55, 95% CI 0.41–0.73). Conclusion Vaccine coverage was high before and after introduction of pentavalent vaccine, but most doses were given late. Coverage is limited by seasonal factors and family size.
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Affiliation(s)
- Moses Ndiritu
- Wellcome Trust/Kenya Medical Research Institute, Centre for Geographic Medicine Research – Coast, Kilifi, Kenya
| | - Karen D Cowgill
- Epidemic Intelligence Service, Epidemiology Program Office, Division of Applied Public Health Training, Centers for Disease Control and Prevention Atlanta, GA, USA
| | - Amina Ismail
- Kenya Expanded Programme on Immunization (KEPI), Ministry of Health, Nairobi, Kenya
| | - Salome Chiphatsi
- Kilifi District Public Health Service, Ministry of Health, Kilifi District Hospital, Kenya
| | - Tatu Kamau
- Kenya Expanded Programme on Immunization (KEPI), Ministry of Health, Nairobi, Kenya
| | - Gregory Fegan
- Wellcome Trust/Kenya Medical Research Institute, Centre for Geographic Medicine Research – Coast, Kilifi, Kenya
- Infectious Diseases Epidemiology Unit, Department of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, University of London, UK
| | - Daniel R Feikin
- Respiratory Diseases Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Charles RJC Newton
- Wellcome Trust/Kenya Medical Research Institute, Centre for Geographic Medicine Research – Coast, Kilifi, Kenya
- Institute of Child Health, University of London, London, UK
| | - J Anthony G Scott
- Wellcome Trust/Kenya Medical Research Institute, Centre for Geographic Medicine Research – Coast, Kilifi, Kenya
- Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford, UK
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15
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Mbugua FM, Okoth FA, Gray M, Kamau T, Kalu A, Eggers R, Borus P, Kombich J, Langat A, Maritim P, Lesiamon J, Tipples GA. Molecular epidemiology of measles virus in Kenya. J Med Virol 2003; 71:599-604. [PMID: 14556275 DOI: 10.1002/jmv.10515] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Measles causes significant morbidity and mortality globally. Many countries have embarked on immunization programs to control and prevent measles outbreaks and eventually to eliminate endemic measles. Kenya is currently in the outbreak control and prevention stage for measles. Measles virus genotyping is important for molecular epidemiological purposes, including the documentation of the elimination of endemic measles virus strains from a country, and mapping of transmission pathways. In this study, we collected clinical specimens from measles outbreak cases in 2002 in Kenya for measles virus genotyping. We were able to isolate and/or detect measles virus in 10 cases from 5 of the 8 provinces in Kenya. All these Kenyan measles strains were determined to be genotype D4 strains when compared to the standard World Health Organization-designated measles virus reference strains. Interestingly, the Kenyan D4 strains clustered into two distinct D4 subgroups. In addition, the inclusion of other published D4 measles strains in this analysis indicated that there are four distinct D4 clusterings, or subgroups: Montreal-like, India-like, Johannesburg-like, and Ethiopia-like. This is the first measles molecular epidemiology study in Kenya and establishes the current endemic measles strain as genotype D4. Importantly, this study shows that the Kenyan D4 strains are distinct from the B3 measles strain found in West Africa and the D4 strains reported in Ethiopia.
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Affiliation(s)
- Francis M Mbugua
- Centre for Virus Research, Kenya Medical Research Institute, Nairobi, Kenya
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16
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Mwatha JK, Kimani G, Kamau T, Mbugua GG, Ouma JH, Mumo J, Fulford AJ, Jones FM, Butterworth AE, Roberts MB, Dunne DW. High levels of TNF, soluble TNF receptors, soluble ICAM-1, and IFN-gamma, but low levels of IL-5, are associated with hepatosplenic disease in human schistosomiasis mansoni. J Immunol 1998; 160:1992-9. [PMID: 9469463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In a case-control study based in two areas of Kenya, hepatosplenic schistosomiasis mansoni was shown to be linked with low levels of IL-5 and with correspondingly high IFN-gamma, TNF, and circulating soluble TNF receptor I (sTNFR-I), sTNFR-II, and sICAM-1. PBMC from the hepatosplenic cases responded to in vitro Ag stimulation with significantly higher levels of IFN-gamma and TNF, but lower levels of IL-5, compared with nonhepatosplenic controls matched for age and infection intensity. Most of these correlations were confounded by differences between geographical areas. However, principle component analysis identified a high IFN-gamma and TNF, and low IL-5 axis in the data as the first principle component; this was significantly associated with hepatosplenomegaly (p < 0.0005) even after controlling for area. High plasma levels of sTNFR-I (p < 0.001), sTNFR-II, (p < 0.0001), and sICAM-1 (p < 0.009) were also significantly associated with hepatosplenomegaly, independently of area, in the case of the soluble forms of both TNF receptors. These parameters were negatively related to IL-5. These results suggest that proinflammatory cytokines are involved in the hepatosplenic disease process in infected individuals who have low anti-inflammatory Th2 responses and that sTNFR may be a useful circulating marker for this disease process, perhaps reflecting the level of TNF activity in hepatic tissues.
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Affiliation(s)
- J K Mwatha
- Kenya Medical Research Institute, Division of Vector Borne Diseases, Nairobi
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17
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Roberts M, Butterworth AE, Kimani G, Kamau T, Fulford AJ, Dunne DW, Ouma JH, Sturrock RF. Immunity after treatment of human schistosomiasis: association between cellular responses and resistance to reinfection. Infect Immun 1993; 61:4984-93. [PMID: 8225573 PMCID: PMC281273 DOI: 10.1128/iai.61.12.4984-4993.1993] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Previous studies have demonstrated the development of an age-dependent resistance to reinfection after chemotherapeutic cure of the helminthic parasite Schistosoma mansoni. Here we report on a longitudinal investigation of cell-mediated responses in infected individuals before and after treatment which was designed to outline those parameters important in mediating a protective response. A well-defined study group of 89 individuals with an age range of 9 to 35 years was selected from an area of high S. mansoni transmission in the Machakos district of Kenya. Peripheral blood mononuclear cell proliferation and cytokine production (interleukin-2 [IL-2], gamma interferon IL-5, IL-4, and tumor necrosis factor) in response to different crude life cycle-stage antigens of S. mansoni were assessed longitudinally in vitro before, 3 months after, and 1 year after treatment. Detailed statistical analyses of the results from this study have indicated a clear negative association between the proliferative responses to adult- and schistosomulum-stage antigens and subsequent reinfection intensity in older individuals (14 to 35 years) which was not present in the younger individuals (9 to 13 years). This association was significant even after the effects of age, sex, and exposure had been accounted for in multiple regression analyses. Cytokines were detected predominantly in response to adult worm and egg antigen extracts. An inverse association between the two cytokines gamma interferon and IL-5 was detected in response to all antigens at the three time points investigated, indicating cross-regulation in the production of these two mediators. Differences in antigen-specific cytokine levels between the two age groups were detected, with significantly higher IL-5 levels detected in the older (more resistant) age group. An inverse correlation between this cytokine and reinfection was detected but could not be dissociated from the effects of age and exposure in multiple regression analysis.
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Affiliation(s)
- M Roberts
- Department of Pathology, Cambridge University, London
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18
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Kimani G, Mkoji GM, Rashid JR, Mbugua JM, Koech D, Kamau T, Mungai B. Enhancement of eosinophil-mediated cytotoxicity to schistosomula of Schistosoma mansoni by autologous mononuclear cells from patients. Parasite Immunol 1993; 15:251-60. [PMID: 8332381 DOI: 10.1111/j.1365-3024.1993.tb00608.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Adherent mononuclear cells (monolayer), when co-cultured with autologous peripheral blood eosinophils isolated from patients treated for Schistosoma mansoni infections, enhanced the eosinophil-mediated killing of antibody coated schistosomula. The monolayer increased the activity of the eosinophils by 225%, and was observed in 80% of the patients studied. Heat labile factors other than complement, present in immune serum, further enhanced the ability of eosinophils to kill schistosomula in the presence of the monolayer. On their own the adherent cells did not mediate obvious damage to the parasite. Eosinophils that had been pre-incubated with the monolayer (100 mins) and tested separately, killed equal numbers of schistosomula as in the co-culture assay; this excludes the possibility of concurrent schistosomula cytotoxicity by the two cell populations. The ability of the monolayer to activate eosinophils was not altered by inhibitors of protein synthesis. The monolayer was largely consistent of monocytes as demonstrated by an over 96% positive staining for non-specific esterases.
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Affiliation(s)
- G Kimani
- Biomedical Sciences Research Centre, Kenya Medical Research Institute, Nairobi
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19
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Abstract
The changes in the immune responses of patients before and at 3 weeks after treatment with anti-schistosomal drugs were investigated. Lymphocyte responses to Concanavalin A and to worm antigens were inhibited after treatment, whereas responses to cercarial and egg antigens remained unchanged. Eosinophil levels were significantly elevated after treatment and were positively correlated with the increase in anti-worm antibodies (r = 0.587), and negatively associated with anti-egg antibodies (r = -0.727). Although the eosinophil-dependent cytotoxicity to schistosomula was not significantly enhanced after treatment, some increased killing was evident of half the patients (7/15). On the other hand, the ability of adherent mononuclear cells to stimulate eosinophil functions was markedly enhanced by treatment (P less than 0.001). These studies suggest that treatment may enhance some of the potentially protective host's immune mechanisms.
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Affiliation(s)
- G Kimani
- Kenya Medical Research Institute, Nairobi
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20
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Kimani G, Chunge CN, Butterworth AE, Kamau T, Bwayo J, Gachihi G, Mungai B, Mugambi M. Eosinophilia and eosinophil helminthotoxicity in patients treated for Schistosoma mansoni infections. Trans R Soc Trop Med Hyg 1991; 85:489-92. [PMID: 1755057 DOI: 10.1016/0035-9203(91)90231-m] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The changes in eosinophil levels and in eosinophil-mediated antibody-dependent schistosomular cytotoxicity, following treatment for Schistosoma mansoni infections, have been investigated in 2 similar groups of patients aged 15-50 years. Patients in group 1 were treated with either hycanthone or oxamniquine, and those in group 2 with hycanthone or praziquantel. Eosinophil levels were significantly increased in both groups. In group 1 peripheral blood eosinophil counts rose from a mean of 175/microliters before treatment to 745/microliters 3 weeks after treatment, and in group 2 from 181/microliters to 1066/microliters. The increase in eosinophil levels was positively correlated with a rise in circulating anti-adult worm antibodies (r = -0.587, P less than 0.05), whereas a negative correlation was recorded with anti-egg antibodies (r = -0.727). Despite some enhanced eosinophil helminthotoxicity following treatment in some of the individuals in group 1 (7/15), the change overall was not significant. In group 2, in which a different standard anti-schistosomular antibody was used, the eosinophil killing capacity recorded at 3 weeks was lower than that before commencement of treatment (t = 2.89, P less than 0.01). The eosinophil stimulating activity, detected in cultured mononuclear cell supernatants (MCS) from individual patients, correlated with eosinophil levels (r = 0.582, P less than 0.02) but there was no association with eosinophil killing. MCS activity did not appear to be boosted by treatment. These studies showed that peripheral blood eosinophil counts were increased following treatment, but their ability to kill schistosome larvae is variable and may depend on the immune serum used as the source of anti-schistosomular antibody.
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Affiliation(s)
- G Kimani
- Biomedical Sciences Centre, Nairobi, Kenya
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21
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Mkoji GM, Njung'e K, Kimani G, Kofi-Tsekpo W, Mungai BN, Kamau T, Muthaura C, Kibaya RM, Wambayi E. Molluscicidal activity of Solanum aculeatum (family: Solanaceae) berries against Biomphalaria pfeifferi, Bulinus globosus and Lymnaea natalensis. Trop Med Parasitol 1989; 40:119-20. [PMID: 2772517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Aqueous suspensions of powder of sun- or freeze-dried berries of the plant Solanum aculeatum (Family Solanaceae), indigenous in Kenya, were tested for molluscicidal activity against Biomphalaria pfeifferi, Bulinus globosus and Lymnaea natalensis under laboratory conditions. One hundred or 50 mg powder L-1 of sun- or freeze-dried berries killed over 60% of the test B. pfeifferi, Bul. globosus and L. natalensis. Whereas 25 mg L-1 of the sun dried material killed less than 60% of the test snails, similar concentrations of the freeze dried molluscicide produced 60-80% mortality in the snails, under similar conditions. Using L. natalensis as the target snail, it was shown that the freeze dried material was more potent than the freeze-dried berries of S. incanum, S. nigrum or leaves of Polygonum senegalensis (Family Polygonaceae), all present in Kenya, and known to possess molluscicidal properties. The powdered material retained molluscicidal activity even after several months storage at room temperature. These findings suggest that S. aculeatum is a potent plant molluscicide, and has the potential for the control of vectors of schistosomiasis and fascioliasis in Kenya.
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Affiliation(s)
- G M Mkoji
- Biomedical Sciences Research Centre, Kenya Medical Research Institute, Nairobi
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22
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Change CN, Kimani G, Gachihi G, Kamau T, Mkoji G, Rashid JR, Wambayi E, Mungai B. Experience with praziquantel at a lower dose in Kenya. Trans R Soc Trop Med Hyg 1987; 81:170-1. [PMID: 3127956 DOI: 10.1016/0035-9203(87)90325-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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23
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Chunge CN, Kimani RG, Gachihi G, Mkoji G, Kamau T, Rashid JR. Serious side effects of oxamniquine during the treatment of Schistosoma mansoni in Kenya. East Afr Med J 1985; 62:3-4. [PMID: 4006813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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