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Gallagher KE, Adetifa IMO, Mburu C, Bottomley C, Akech D, Karani A, Pearce E, Wang Y, Kagucia EW, Goldblatt D, Hammitt LL, Scott JAG. Population immunity to pneumococcal serotypes in Kilifi, Kenya, before and 6 years after the introduction of PCV10 with a catch-up campaign: an observational study of cross-sectional serosurveys. Lancet Infect Dis 2023; 23:1291-1301. [PMID: 37429307 DOI: 10.1016/s1473-3099(23)00206-2] [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] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 03/13/2023] [Accepted: 03/27/2023] [Indexed: 07/12/2023]
Abstract
BACKGROUND In Kilifi (Kenya), a pneumococcal conjugate vaccine (PCV10) was introduced in 2011 in infants (aged <1 year, 3 + 0 schedule) with a catch-up campaign in children aged 1-4 years. We aimed to measure the effect of PCV10 on population immunity. METHODS In this observational study, repeated cross-sectional serosurveys were conducted in independent random samples of 500 children younger than 15 years every 2 years between 2009 and 2017. During these surveys, blood samples were collected by venesection. Concentrations of anti-capsular IgGs against vaccine serotypes (VTs) 1, 4, 5, 6B, 7F, 9V, 14, 18C, 19F, and 23F, and against serotypes 6A and 19A, were assayed by ELISA. We plotted the geometric mean concentrations (GMCs) by birth year to visualise age-specific antibody profiles. In infants, IgG concentrations of 0·35 μg/mL or higher were considered protective. FINDINGS Of 3673 volunteers approached, 2152 submitted samples for analysis across the five surveys. Vaccine introduction resulted in an increase in the proportion of young children with protective IgG concentrations, compared with before vaccine introduction (from 0-33% of infants with VT-specific levels over the correlate of protection in 2009, to 60-94% of infants in 2011). However, among those vaccinated in infancy, GMCs of all ten VTs had waned rapidly by the age of 1, but rose again later in childhood. GMCs among children aged 10-14 years were consistently high over time (eg, the range of GMCs across survey rounds were between 0·45 μg/mL and 1·00 μg/mL for VT 23F and between 2·00 μg/mL and 3·11 μg/mL for VT 19F). INTERPRETATION PCV10 in a 3 + 0 schedule elicited protective IgG levels during infancy, when disease risk is high. The high antibody levels in children aged 10-14 years might indicate continued exposure to vaccine serotypes due to residual carriage or to memory responses to cross-reactive antigens. Despite rapid waning of IgG after vaccination, disease incidence among young children in this setting remains low, suggesting that lower thresholds of antibody, or other markers of immunity (eg, memory B cells), may be needed to assess population protection among children who have aged past infancy. FUNDING Gavi, the Vaccine Alliance; Wellcome Trust.
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Affiliation(s)
- Katherine E Gallagher
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK.
| | - Ifedayo M O Adetifa
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK
| | | | - Christian Bottomley
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK
| | - Donald Akech
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Angela Karani
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Emma Pearce
- Great Ormond Street Institute of Child Health, University College London, London, UK
| | - Yanyun Wang
- Great Ormond Street Institute of Child Health, University College London, London, UK
| | | | - David Goldblatt
- Great Ormond Street Institute of Child Health, University College London, London, UK
| | - Laura L Hammitt
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Department of International Health, International Vaccine Access Center, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - J Anthony G Scott
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK
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Kagucia EW, Ziraba AK, Nyagwange J, Kutima B, Kimani M, Akech D, Ng'oda M, Sigilai A, Mugo D, Karanja H, Gitonga J, Karani A, Toroitich M, Karia B, Otiende M, Njeri A, Aman R, Amoth P, Mwangangi M, Kasera K, Ng'ang'a W, Voller S, Ochola‐Oyier LI, Bottomley C, Nyaguara A, Munywoki PK, Bigogo G, Maitha E, Uyoga S, Gallagher KE, Etyang AO, Barasa E, Mwangangi J, Bejon P, Adetifa IMO, Warimwe GM, Scott JAG, Agweyu A. SARS-CoV-2 seroprevalence and implications for population immunity: Evidence from two Health and Demographic Surveillance System sites in Kenya, February-December 2022. Influenza Other Respir Viruses 2023; 17:e13173. [PMID: 37752065 PMCID: PMC10522478 DOI: 10.1111/irv.13173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 06/19/2023] [Accepted: 06/28/2023] [Indexed: 09/28/2023] Open
Abstract
BACKGROUND We sought to estimate SARS-CoV-2 antibody seroprevalence within representative samples of the Kenyan population during the third year of the COVID-19 pandemic and the second year of COVID-19 vaccine use. METHODS We conducted cross-sectional serosurveys among randomly selected, age-stratified samples of Health and Demographic Surveillance System (HDSS) residents in Kilifi and Nairobi. Anti-spike (anti-S) immunoglobulin G (IgG) serostatus was measured using a validated in-house ELISA and antibody concentrations estimated with reference to the WHO International Standard for anti-SARS-CoV-2 immunoglobulin. RESULTS HDSS residents were sampled in February-June 2022 (Kilifi HDSS N = 852; Nairobi Urban HDSS N = 851) and in August-December 2022 (N = 850 for both sites). Population-weighted coverage for ≥1 doses of COVID-19 vaccine were 11.1% (9.1-13.2%) among Kilifi HDSS residents by November 2022 and 34.2% (30.7-37.6%) among Nairobi Urban HDSS residents by December 2022. Population-weighted anti-S IgG seroprevalence among Kilifi HDSS residents increased from 69.1% (65.8-72.3%) by May 2022 to 77.4% (74.4-80.2%) by November 2022. Within the Nairobi Urban HDSS, seroprevalence by June 2022 was 88.5% (86.1-90.6%), comparable with seroprevalence by December 2022 (92.2%; 90.2-93.9%). For both surveys, seroprevalence was significantly lower among Kilifi HDSS residents than among Nairobi Urban HDSS residents, as were antibody concentrations (p < 0.001). CONCLUSION More than 70% of Kilifi residents and 90% of Nairobi residents were seropositive for anti-S IgG by the end of 2022. There is a potential immunity gap in rural Kenya; implementation of interventions to improve COVID-19 vaccine uptake among sub-groups at increased risk of severe COVID-19 in rural settings is recommended.
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Affiliation(s)
| | | | | | | | | | - Donald Akech
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
| | - Maurine Ng'oda
- African Population and Health Research CenterNairobiKenya
| | | | - Daisy Mugo
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
| | | | - John Gitonga
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
| | | | | | | | - Mark Otiende
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
| | - Anne Njeri
- African Population and Health Research CenterNairobiKenya
| | | | | | | | | | - Wangari Ng'ang'a
- Presidential Policy and Strategy UnitThe Presidency, Government of KenyaNairobiKenya
| | - Shirine Voller
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
- London School of Hygiene and Tropical MedicineLondonUK
| | | | | | | | - Patrick K. Munywoki
- Division for Global Health ProtectionUS Centers of Disease Control and Prevention, Center for Global HealthNairobiKenya
| | | | | | - Sophie Uyoga
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
| | - Katherine E. Gallagher
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
- London School of Hygiene and Tropical MedicineLondonUK
| | | | | | | | - Philip Bejon
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of MedicineOxford UniversityOxfordUK
| | - Ifedayo M. O. Adetifa
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
- London School of Hygiene and Tropical MedicineLondonUK
| | - George M. Warimwe
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of MedicineOxford UniversityOxfordUK
| | - J. Anthony G. Scott
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
- London School of Hygiene and Tropical MedicineLondonUK
| | - Ambrose Agweyu
- KEMRI‐Wellcome Trust Research ProgrammeKilifiKenya
- London School of Hygiene and Tropical MedicineLondonUK
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Butler MEB, Jansen van Rensburg MJ, Karani A, Mvera B, Akech D, Akter A, Forrest C, van Tonder AJ, Quirk SJ, Haraldsson G, Bentley SD, Erlendsdóttir H, Haraldsson Á, Kristinsson KG, Scott JAG, Brueggemann AB. Nasopharyngeal competition dynamics are likely to be altered following vaccine introduction: bacteriocin prevalence and diversity among Icelandic and Kenyan pneumococci. Microb Genom 2023; 9:mgen001060. [PMID: 37436819 PMCID: PMC10438807 DOI: 10.1099/mgen.0.001060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 06/09/2023] [Indexed: 07/13/2023] Open
Abstract
Bacteriocins are antimicrobial peptides produced by bacteria to inhibit other bacteria in the surrounding environment. Streptococcus pneumoniae is a leading cause of disease worldwide and colonises the healthy human nasopharynx, where it competes for space and nutrients. Pneumococcal conjugate vaccines have reduced the incidence of disease, but they also restructure the bacterial population, and this restructuring likely alters the nasopharyngeal competition dynamics. Here, the distribution of bacteriocins was examined in over 5000 carriage and disease-causing pneumococci from Iceland and Kenya, recovered before and after the introduction of pneumococcal vaccination. Overall, up to eleven different bacteriocin gene clusters were identified per pneumococcus. Significant differences in the prevalence of bacteriocins were observed before and after vaccine introduction, and among carriage and disease-causing pneumococci, which were largely explained by the bacterial population structure. Genetically similar pneumococci generally harboured the same bacteriocins although sometimes different repertoires of bacteriocins were observed, which suggested that horizontal transfer of bacteriocin clusters had occurred. These findings demonstrated that vaccine-mediated changes in the pneumococcal population altered the prevalence and distribution of bacteriocins. The consequences of this for pneumococcal colonisation and disease remain to be determined.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Sigríður J. Quirk
- University of Iceland and Landspitali - The National University Hospital of Iceland, Reykjavík, Iceland
| | - Gunnsteinn Haraldsson
- University of Iceland and Landspitali - The National University Hospital of Iceland, Reykjavík, Iceland
| | | | - Helga Erlendsdóttir
- University of Iceland and Landspitali - The National University Hospital of Iceland, Reykjavík, Iceland
| | - Ásgeir Haraldsson
- University of Iceland and Children’s Hospital Iceland, Landspitali, Reykjavík, Iceland
| | - Karl G. Kristinsson
- University of Iceland and Landspitali - The National University Hospital of Iceland, Reykjavík, Iceland
| | - J. Anthony G. Scott
- KEMRI Wellcome Trust Programme, Kilifi, Kenya
- London School of Hygiene and Tropical Medicine, London, UK
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Adamu AL, Ojal J, Abubakar IA, Odeyemi KA, Bello MM, Okoromah CAN, Karia B, Karani A, Akech D, Inem V, Scott JAG, Adetifa IMO. The impact of introduction of the 10-valent pneumococcal conjugate vaccine on pneumococcal carriage in Nigeria. Nat Commun 2023; 14:2666. [PMID: 37160867 PMCID: PMC10169786 DOI: 10.1038/s41467-023-38277-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 04/24/2023] [Indexed: 05/11/2023] Open
Abstract
Pneumococcal conjugate vaccines (PCVs) protect against invasive pneumococcal disease (IPD) among vaccinees. However, at population level, this protection is driven by indirect effects. PCVs prevent nasopharyngeal acquisition of vaccine-serotype (VT) pneumococci, reducing onward transmission. Each disease episode is preceded by infection from a carrier, so vaccine impacts on carriage provide a minimum estimate of disease reduction in settings lacking expensive IPD surveillance. We documented carriage prevalence and vaccine coverage in two settings in Nigeria annually (2016-2020) following PCV10 introduction in 2016. Among 4,684 rural participants, VT carriage prevalence fell from 21 to 12% as childhood (<5 years) vaccine coverage rose from 7 to 84%. Among 2,135 urban participants, VT carriage prevalence fell from 16 to 9% as uptake rose from 15 to 94%. Within these ranges, carriage prevalence declined with uptake. Increasing PCV10 coverage reduced pneumococcal infection at all ages, implying at least a comparable reduction in IPD.
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Affiliation(s)
- Aishatu L Adamu
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.
- Department of Infectious Diseases Epidemiology, London School of Hygiene & Tropical Medicine, London, UK.
- Department of Community Medicine, College of Health Sciences, Bayero University, Kano/Aminu Kano Teaching Hospital, Kano, Nigeria.
| | - J Ojal
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Department of Infectious Diseases Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Isa A Abubakar
- Department of Community Medicine, College of Health Sciences, Bayero University, Kano/Aminu Kano Teaching Hospital, Kano, Nigeria
| | - Kofo A Odeyemi
- Department of Community Medicine and Primary Care, College of Medicine, University of Lagos, Lagos, Nigeria
| | - Musa M Bello
- Department of Community Medicine, College of Health Sciences, Bayero University, Kano/Aminu Kano Teaching Hospital, Kano, Nigeria
| | - Christy A N Okoromah
- Department of Paediatrics and Child Health, College of Medicine, University of Lagos, Lagos, Nigeria
| | | | - Angela Karani
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Donald Akech
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Victor Inem
- Department of Community Medicine and Primary Care, College of Medicine, University of Lagos, Lagos, Nigeria
| | - J Anthony G Scott
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Department of Infectious Diseases Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Ifedayo M O Adetifa
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Department of Infectious Diseases Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
- Department of Paediatrics and Child Health, College of Medicine, University of Lagos, Lagos, Nigeria
- Nigeria Centre for Disease Control, Abuja, Nigeria
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Etyang AO, Adetifa I, Omore R, Misore T, Ziraba AK, Ng’oda MA, Gitau E, Gitonga J, Mugo D, Kutima B, Karanja H, Toroitich M, Nyagwange J, Tuju J, Wanjiku P, Aman R, Amoth P, Mwangangi M, Kasera K, Ng’ang’a W, Akech D, Sigilai A, Karia B, Karani A, Voller S, Agoti CN, Ochola-Oyier LI, Otiende M, Bottomley C, Nyaguara A, Uyoga S, Gallagher K, Kagucia EW, Onyango D, Tsofa B, Mwangangi J, Maitha E, Barasa E, Bejon P, Warimwe GM, Scott JAG, Agweyu A. SARS-CoV-2 seroprevalence in three Kenyan health and demographic surveillance sites, December 2020-May 2021. PLOS Glob Public Health 2022; 2:e0000883. [PMID: 36962821 PMCID: PMC10021917 DOI: 10.1371/journal.pgph.0000883] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 07/12/2022] [Indexed: 11/19/2022]
Abstract
BACKGROUND Most of the studies that have informed the public health response to the COVID-19 pandemic in Kenya have relied on samples that are not representative of the general population. We conducted population-based serosurveys at three Health and Demographic Surveillance Systems (HDSSs) to determine the cumulative incidence of infection with SARS-CoV-2. METHODS We selected random age-stratified population-based samples at HDSSs in Kisumu, Nairobi and Kilifi, in Kenya. Blood samples were collected from participants between 01 Dec 2020 and 27 May 2021. No participant had received a COVID-19 vaccine. We tested for IgG antibodies to SARS-CoV-2 spike protein using ELISA. Locally-validated assay sensitivity and specificity were 93% (95% CI 88-96%) and 99% (95% CI 98-99.5%), respectively. We adjusted prevalence estimates using classical methods and Bayesian modelling to account for the sampling scheme and assay performance. RESULTS We recruited 2,559 individuals from the three HDSS sites, median age (IQR) 27 (10-78) years and 52% were female. Seroprevalence at all three sites rose steadily during the study period. In Kisumu, Nairobi and Kilifi, seroprevalences (95% CI) at the beginning of the study were 36.0% (28.2-44.4%), 32.4% (23.1-42.4%), and 14.5% (9.1-21%), and respectively; at the end they were 42.0% (34.7-50.0%), 50.2% (39.7-61.1%), and 24.7% (17.5-32.6%), respectively. Seroprevalence was substantially lower among children (<16 years) than among adults at all three sites (p≤0.001). CONCLUSION By May 2021 in three broadly representative populations of unvaccinated individuals in Kenya, seroprevalence of anti-SARS-CoV-2 IgG was 25-50%. There was wide variation in cumulative incidence by location and age.
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Affiliation(s)
| | - Ifedayo Adetifa
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Richard Omore
- Kenya Medical Research Institute Centre for Global Health Research, Kisumu, Kenya
| | - Thomas Misore
- Kenya Medical Research Institute Centre for Global Health Research, Kisumu, Kenya
| | | | | | - Evelyn Gitau
- African Population and Health Research Center, Nairobi, Kenya
| | - John Gitonga
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Daisy Mugo
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | - Henry Karanja
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | | | - James Tuju
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | | | | | | | | | - Wangari Ng’ang’a
- Presidential Policy and Strategy Unit, The Presidency, Government of Kenya, Nairobi, Kenya
| | - Donald Akech
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | | | - Angela Karani
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Shirine Voller
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | | | | | - Mark Otiende
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | - Amek Nyaguara
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Sophie Uyoga
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | | | | | | | | | | | - Edwine Barasa
- Health Economics Research Unit, KEMRI-Wellcome Trust Research Programme, Nairobi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, Oxford University, Oxford, United Kingdom
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, Oxford University, Oxford, United Kingdom
| | - George M. Warimwe
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, Oxford University, Oxford, United Kingdom
| | - J. Anthony G. Scott
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- London School of Hygiene and Tropical Medicine, London, United Kingdom
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Mburu CN, Ojal J, Chebet R, Akech D, Karia B, Tuju J, Sigilai A, Abbas K, Jit M, Funk S, Smits G, van Gageldonk PGM, van der Klis FRM, Tabu C, Nokes DJ, Scott J, Flasche S, Adetifa I. The importance of supplementary immunisation activities to prevent measles outbreaks during the COVID-19 pandemic in Kenya. BMC Med 2021; 19:35. [PMID: 33531015 PMCID: PMC7854026 DOI: 10.1186/s12916-021-01906-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 01/11/2021] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The COVID-19 pandemic has disrupted routine measles immunisation and supplementary immunisation activities (SIAs) in most countries including Kenya. We assessed the risk of measles outbreaks during the pandemic in Kenya as a case study for the African Region. METHODS Combining measles serological data, local contact patterns, and vaccination coverage into a cohort model, we predicted the age-adjusted population immunity in Kenya and estimated the probability of outbreaks when contact-reducing COVID-19 interventions are lifted. We considered various scenarios for reduced measles vaccination coverage from April 2020. RESULTS In February 2020, when a scheduled SIA was postponed, population immunity was close to the herd immunity threshold and the probability of a large outbreak was 34% (8-54). As the COVID-19 contact restrictions are nearly fully eased, from December 2020, the probability of a large measles outbreak will increase to 38% (19-54), 46% (30-59), and 54% (43-64) assuming a 15%, 50%, and 100% reduction in measles vaccination coverage. By December 2021, this risk increases further to 43% (25-56), 54% (43-63), and 67% (59-72) for the same coverage scenarios respectively. However, the increased risk of a measles outbreak following the lifting of all restrictions can be overcome by conducting a SIA with ≥ 95% coverage in under-fives. CONCLUSION While contact restrictions sufficient for SAR-CoV-2 control temporarily reduce measles transmissibility and the risk of an outbreak from a measles immunity gap, this risk rises rapidly once these restrictions are lifted. Implementing delayed SIAs will be critical for prevention of measles outbreaks given the roll-back of contact restrictions in Kenya.
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Affiliation(s)
- C N Mburu
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.
- Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.
| | - J Ojal
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - R Chebet
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - D Akech
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - B Karia
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - J Tuju
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - A Sigilai
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - K Abbas
- Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - M Jit
- Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - S Funk
- Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - G Smits
- Department of Immunosurveillance, Centre for Infectious Diseases Control, National Institute of Public Health and the Environment (RIVM), Bilthoven, The Netherlands
| | - P G M van Gageldonk
- Department of Immunosurveillance, Centre for Infectious Diseases Control, National Institute of Public Health and the Environment (RIVM), Bilthoven, The Netherlands
| | - F R M van der Klis
- Department of Immunosurveillance, Centre for Infectious Diseases Control, National Institute of Public Health and the Environment (RIVM), Bilthoven, The Netherlands
| | - C Tabu
- National Vaccine and Immunisation Programme, Ministry of Health, Nairobi, Kenya
| | - D J Nokes
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- School of Life Sciences and Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research (SBIDER), University of Warwick, Coventry, UK
| | - Jag Scott
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - S Flasche
- Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - Imo Adetifa
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.
- Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.
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7
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Ojal J, Griffiths U, Hammitt LL, Adetifa I, Akech D, Tabu C, Scott JAG, Flasche S. Sustaining pneumococcal vaccination after transitioning from Gavi support: a modelling and cost-effectiveness study in Kenya. Lancet Glob Health 2019; 7:e644-e654. [PMID: 31000132 PMCID: PMC6484775 DOI: 10.1016/s2214-109x(18)30562-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [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: 04/06/2018] [Revised: 12/03/2018] [Accepted: 12/06/2018] [Indexed: 11/29/2022]
Abstract
BACKGROUND In 2009, Gavi, the World Bank, and donors launched the pneumococcal Advance Market Commitment, which helped countries access more affordable pneumococcal vaccines. As many low-income countries begin to reach the threshold at which countries transition from Gavi support to self-financing (3-year average gross national income per capita of US$1580), they will need to consider whether to continue pneumococcal conjugate vaccine (PCV) use at full cost or to discontinue PCV in their childhood immunisation programmes. Using Kenya as a case study, we assessed the incremental cost-effectiveness of continuing PCV use. METHODS In this modelling and cost-effectiveness study, we fitted a dynamic compartmental model of pneumococcal carriage to annual carriage prevalence surveys and invasive pneumococcal disease (IPD) incidence in Kilifi, Kenya. We predicted disease incidence and related mortality for either continuing PCV use beyond 2022, the start of Kenya's transition from Gavi support, or its discontinuation. We calculated the costs per disability-adjusted life-year (DALY) averted and associated 95% prediction intervals (PI). FINDINGS We predicted that if PCV use is discontinued in Kenya in 2022, overall IPD incidence will increase from 8·5 per 100 000 in 2022, to 16·2 per 100 000 per year in 2032. Continuing vaccination would prevent 14 329 (95% PI 6130-25 256) deaths and 101 513 (4386-196 674) disease cases during that time. Continuing PCV after 2022 will require an estimated additional US$15·8 million annually compared with discontinuing vaccination. We predicted that the incremental cost per DALY averted of continuing PCV would be $153 (95% PI 70-411) in 2032. INTERPRETATION Continuing PCV use is essential to sustain its health gains. Based on the Kenyan GDP per capita of $1445, and in comparison to other vaccines, continued PCV use at full costs is cost-effective (on the basis of the assumption that any reduction in disease will translate to a reduction in mortality). Although affordability is likely to be a concern, our findings support an expansion of the vaccine budget in Kenya. FUNDING Wellcome Trust and Gavi, the Vaccine Alliance.
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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 & Tropical Medicine, London, UK.
| | - Ulla Griffiths
- Department of Global Health and Development, London School of Hygiene & Tropical Medicine, London, UK; UNICEF Health Section, Programme Division, New York, NY, USA
| | - 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
| | - 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 & Tropical Medicine, London, UK
| | - Donald Akech
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | | | - 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 & Tropical Medicine, London, UK
| | - Stefan Flasche
- Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK
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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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