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Tukwasibwe S, Mboowa G, Sserwadda I, Nankabirwa JI, Arinaitwe E, Ssewanyana I, Taremwa Y, Tumusiime G, Kamya MR, Jagannathan P, Nakimuli A. Impact of high human genetic diversity in Africa on immunogenicity and efficacy of RTS,S/AS01 vaccine. Immunogenetics 2023; 75:207-214. [PMID: 37084013 PMCID: PMC10119520 DOI: 10.1007/s00251-023-01306-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 04/06/2023] [Indexed: 04/22/2023]
Abstract
In modern medicine, vaccination is one of the most effective public health strategies to prevent infectious diseases. Indisputably, vaccines have saved millions of lives by reducing the burden of many serious infections such as polio, tuberculosis, measles, pneumonia, and tetanus. Despite the recent recommendation by the World Health Organization (WHO) to roll out RTS,S/AS01, this malaria vaccine still faces major challenges of variability in its efficacy partly due to high genetic variation in humans and malaria parasites. Immune responses to malaria vary between individuals and populations. Human genetic variation in immune system genes is the probable cause for this heterogeneity. In this review, we will focus on human genetic factors that determine variable responses to vaccination and how variation in immune system genes affect the immunogenicity and efficacy of the RTS,S/AS01 vaccine.
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Affiliation(s)
- Stephen Tukwasibwe
- Infectious Diseases Research Collaboration, Kampala, Uganda.
- Infectious Diseases Institute, College of Health Sciences, Makerere University, Kampala, Uganda.
- School of Medicine, Uganda Christian University, Kampala, Uganda.
| | - Gerald Mboowa
- Infectious Diseases Institute, College of Health Sciences, Makerere University, Kampala, Uganda
| | - Ivan Sserwadda
- Infectious Diseases Institute, College of Health Sciences, Makerere University, Kampala, Uganda
| | | | | | | | - Yoweri Taremwa
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Gerald Tumusiime
- School of Medicine, Uganda Christian University, Kampala, Uganda
| | - Moses R Kamya
- Infectious Diseases Research Collaboration, Kampala, Uganda
- School of Medicine, College of Health Sciences, Makerere University, Kampala, Uganda
| | | | - Annettee Nakimuli
- School of Medicine, College of Health Sciences, Makerere University, Kampala, Uganda
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Mategula D, Mitambo C, Sheahan W, Masingi Mbeye N, Gumbo A, Kwizombe C, Kawonga J, Banda B, Hamuza G, Kalanga A, Kamowa D, Kafulafula J, Banda A, Twaibi H, Musa E, Kapito-Tembo A, Ntwere T, Chirombo J, Kalonde PK, Masambuka M, Munthali L, Sakala M, Bangoura A, Gichuki J, Chipeta MG, Galatas Adrade B, Kayange M, Terlouw DJ. Malaria Burden Stratification in Malawi- A report of a consultative workshop to inform the 2023-2030 Malawi Malaria Strategic Plan. Wellcome Open Res 2023; 8:178. [PMID: 37600585 PMCID: PMC10432890 DOI: 10.12688/wellcomeopenres.19110.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/05/2023] [Indexed: 08/22/2023] Open
Abstract
Background: Malawi's National Malaria Control Programme (NMCP) is developing a new strategic plan for 2023-2030 to combat malaria and recognizes that a blanket approach to malaria interventions is no longer feasible. To inform this new strategy, the NMCP set up a task force comprising 18 members from various sectors, which convened a meeting to stratify the malaria burden in Malawi and recommend interventions for each stratum. Methods: The burden stratification workshop took place from November 29 to December 2, 2022, in Blantyre, Malawi, and collated essential data on malaria burden indicators, such as incidence, prevalence, and mortality. Workshop participants reviewed the malaria burden and intervention coverage data to describe the current status and identified the districts as a appropriate administrative level for stratification and action. Two scenarios were developed for the stratification, based on composites of three variables. Scenario 1 included incidence, prevalence, and under-five all-cause mortality, while Scenario 2 included total malaria cases, prevalence, and under-five all-cause mortality counts. The task force developed four burden strata (highest, high, moderate, and low) for each scenario, resulting in a final list of districts assigned to each stratum. Results: The task force concluded with 10 districts in the highest-burden stratum (Nkhotakota, Salima, Mchinji, Dowa, Ntchisi, Mwanza, Likoma, Lilongwe, Kasungu and Mangochi) 11 districts in the high burden stratum (Chitipa, Rumphi, Nkhata Bay, Dedza, Ntcheu, Neno, Thyolo, Nsanje, Zomba, Mzimba and Mulanje) and seven districts in the moderate burden stratum (Karonga, Chikwawa, Balaka, Machinga, Phalombe, Blantyre, and Chiradzulu). There were no districts in the low-burden stratum. Conclusion: The next steps for the NMCP are to review context-specific issues driving malaria transmission and recommend interventions for each stratum. Overall, this burden stratification workshop provides a critical foundation for developing a successful malaria strategic plan for Malawi.
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Affiliation(s)
- Donnie Mategula
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
- Malawi-Liverpool Wellcome Programme,, Blantyre, Malawi
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | | | | | - Nyanyiwe Masingi Mbeye
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
- PATH, Seatle, Washington, USA
| | - Austin Gumbo
- National Malaria Control Programme, Ministry of Health, Lilongwe, Malawi
| | - Collins Kwizombe
- U.S. President's Malaria Initiative, United States Agency for International Development (USAID), Lilongwe, Malawi
| | - Jacob Kawonga
- Country Health Information Systems and Data Use (CHISU) Program, Lilongwe, Malawi
| | - Benard Banda
- Country Health Information Systems and Data Use (CHISU) Program, Lilongwe, Malawi
| | - Gracious Hamuza
- National Malaria Control Programme, Ministry of Health, Lilongwe, Malawi
| | | | - Dina Kamowa
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | | | - Akuzike Banda
- National Malaria Control Programme, Ministry of Health, Lilongwe, Malawi
| | - Halima Twaibi
- Department of Mathematical Sciences, School of Natural and Applied Sciences,, University of Malawi, Zomba, Malawi
| | - Esloyn Musa
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Atupele Kapito-Tembo
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Tapiwa Ntwere
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | | | - Patrick, Ken Kalonde
- Malawi-Liverpool Wellcome Programme,, Blantyre, Malawi
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | | | - Lumbani Munthali
- National Malaria Control Programme, Ministry of Health, Lilongwe, Malawi
| | - Melody Sakala
- Malawi-Liverpool Wellcome Programme,, Blantyre, Malawi
| | | | - Judy Gichuki
- Strathmore University, Institute of Healthcare Management, Nairobi, Malawi
| | | | | | - Michael Kayange
- National Malaria Control Programme, Ministry of Health, Lilongwe, Malawi
| | - Dianne J Terlouw
- Malawi-Liverpool Wellcome Programme,, Blantyre, Malawi
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
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Topazian HM, Schmit N, Gerard-Ursin I, Charles GD, Thompson H, Ghani AC, Winskill P. Modelling the relative cost-effectiveness of the RTS,S/AS01 malaria vaccine compared to investment in vector control or chemoprophylaxis. Vaccine 2023; 41:3215-3223. [PMID: 37080831 DOI: 10.1016/j.vaccine.2023.04.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 04/03/2023] [Accepted: 04/03/2023] [Indexed: 04/22/2023]
Abstract
BACKGROUND The World Health Organization has recommended a 4-dose schedule of the RTS,S/AS01 (RTS,S) vaccine for children in regions of moderate to high P. falciparum transmission. Faced with limited supply and finite resources, global funders and domestic malaria control programs will need to examine the relative cost-effectiveness of RTS,S and identify target areas for vaccine implementation relative to scale-up of existing interventions. METHODS Using an individual-based mathematical model of P. falciparum, we modelled the cost-effectiveness of RTS,S across a range of settings in sub-Saharan Africa, incorporating various rainfall patterns, insecticide-treated net (ITN) use, treatment coverage, and parasite prevalence bands. We compare age-based and seasonal RTS,S administration to increasing ITN usage, switching to next generation ITNs in settings experiencing insecticide-resistance, and introduction of seasonal malaria chemoprevention (SMC) in areas of seasonal transmission. RESULTS For RTS,S to be the most cost-effective intervention option considered, the maximum cost per dose was less than $9.30 USD in 90.9% of scenarios. Nearly all (89.8%) values at or above $9.30 USD per dose were in settings with 60% established bed net use and / or with established SMC, and 76.3% were in the highest PfPR2-10 band modelled (40%). Addition of RTS,S to strategies involving 60% ITN use, increased ITN usage or a switch to PBO nets, and SMC, if eligible, still led to significant marginal case reductions, with a median of 2,653 (IQR: 1,741 to 3,966) cases averted per 100,000 people annually, and 82,270 (IQR: 54,034 to 123,105) cases averted per 100,000 fully vaccinated children (receiving at least three doses). CONCLUSIONS Use of RTS,S results in reductions in malaria cases and deaths even when layered upon existing interventions. When comparing relative cost-effectiveness, scale up of ITNs, introduction of SMC, and switching to new technology nets should be prioritized in eligible settings.
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Affiliation(s)
- Hillary M Topazian
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK.
| | - Nora Schmit
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK
| | - Ines Gerard-Ursin
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK
| | - Giovanni D Charles
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK
| | - Hayley Thompson
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK
| | - Azra C Ghani
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK
| | - Peter Winskill
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK
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Patikorn C, Cho JY, Lambach P, Hutubessy R, Chaiyakunapruk N. Equity-Informative Economic Evaluations of Vaccines: A Systematic Literature Review. Vaccines (Basel) 2023; 11:622. [PMID: 36992206 PMCID: PMC10057152 DOI: 10.3390/vaccines11030622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 03/01/2023] [Accepted: 03/02/2023] [Indexed: 03/12/2023] Open
Abstract
The Immunization Agenda 2030 prioritizes the populations without access to vaccines. Health equity has been increasingly incorporated into economic evaluations of vaccines to foster equitable access. Robust and standardized methods are needed to evaluate the health equity impact of vaccination programs to ensure monitoring and effective addressing of inequities. However, methods currently in place vary and potentially affect the application of findings to inform policy decision-making. We performed a systematic review by searching PubMed, Embase, Econlit, and the CEA Registry up to 15 December 2022 to identify equity-informative economic evaluations of vaccines. Twenty-one studies were included that performed health equity impact analysis to estimate the distributional impact of vaccines, such as deaths averted and financial risk protection, across equity-relevant subgroups. These studies showed that the introduction of vaccines or improved vaccination coverage resulted in fewer deaths and higher financial risk benefits in subpopulations with higher disease burdens and lower vaccination coverage-particularly poorer income groups and those living in rural areas. In conclusion, methods to incorporate equity have been evolving progressively. Vaccination programs can enhance equity if their design and implementation address existing inequities in order to provide equitable vaccination coverage and achieve health equity.
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Affiliation(s)
- Chanthawat Patikorn
- Department of Pharmacotherapy, College of Pharmacy, University of Utah, Salt Lake City, UT 84112, USA
- Department of Social and Administrative Pharmacy, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok 10540, Thailand
| | - Jeong-Yeon Cho
- Department of Pharmacotherapy, College of Pharmacy, University of Utah, Salt Lake City, UT 84112, USA
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Philipp Lambach
- Department of Immunization, Vaccines and Biologicals (IVB), World Health Organization, 1211 Geneva, Switzerland
| | - Raymond Hutubessy
- Department of Immunization, Vaccines and Biologicals (IVB), World Health Organization, 1211 Geneva, Switzerland
| | - Nathorn Chaiyakunapruk
- Department of Pharmacotherapy, College of Pharmacy, University of Utah, Salt Lake City, UT 84112, USA
- IDEAS Center, Veterans Affairs Salt Lake City Healthcare System, Salt Lake City, UT 84112, USA
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Bell GJ, Goel V, Essone P, Dosoo D, Adu B, Mensah BA, Gyaase S, Wiru K, Mougeni F, Osei M, Minsoko P, Sinai C, Niaré K, Juliano JJ, Hudgens M, Ghansah A, Kamthunzi P, Mvalo T, Agnandji ST, Bailey JA, Asante KP, Emch M. Malaria Transmission Intensity Likely Modifies RTS, S/AS01 Efficacy Due to a Rebound Effect in Ghana, Malawi, and Gabon. J Infect Dis 2022; 226:1646-1656. [PMID: 35899811 PMCID: PMC10205900 DOI: 10.1093/infdis/jiac322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 07/26/2022] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND RTS,S/AS01 is the first malaria vaccine to be approved and recommended for widespread implementation by the World Health Organization (WHO). Trials reported lower vaccine efficacies in higher-incidence sites, potentially due to a "rebound" in malaria cases in vaccinated children. When naturally acquired protection in the control group rises and vaccine protection in the vaccinated wanes concurrently, malaria incidence can become greater in the vaccinated than in the control group, resulting in negative vaccine efficacies. METHODS Using data from the 2009-2014 phase III trial (NCT00866619) in Lilongwe, Malawi; Kintampo, Ghana; and Lambaréné, Gabon, we evaluate this hypothesis by estimating malaria incidence in each vaccine group over time and in varying transmission settings. After estimating transmission intensities using ecological variables, we fit models with 3-way interactions between vaccination, time, and transmission intensity. RESULTS Over time, incidence decreased in the control group and increased in the vaccine group. Three-dose efficacy in the lowest-transmission-intensity group (0.25 cases per person-year [CPPY]) decreased from 88.2% to 15.0% over 4.5 years, compared with 81.6% to -27.7% in the highest-transmission-intensity group (3 CPPY). CONCLUSIONS These findings suggest that interventions, including the fourth RTS,S dose, that protect vaccinated individuals during the potential rebound period should be implemented for high-transmission settings.
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Affiliation(s)
- Griffin J Bell
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Varun Goel
- Carolina Population Center, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Paulin Essone
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
| | - David Dosoo
- Kintampo Health Research Centre, Kintampo, Ghana
| | - Bright Adu
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | | | | | - Kenneth Wiru
- Kintampo Health Research Centre, Kintampo, Ghana
| | - Fabrice Mougeni
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
| | - Musah Osei
- Kintampo Health Research Centre, Kintampo, Ghana
| | - Pamela Minsoko
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
| | - Cyrus Sinai
- Carolina Population Center, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Karamoko Niaré
- Department of Pathology and Laboratory Medicine, Brown University, Providence, Rhode Island, USA
| | - Jonathan J Juliano
- Division of Infectious Diseases, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Michael Hudgens
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Anita Ghansah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | | | | | - Selidji Todagbe Agnandji
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
- Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany
| | - Jeffrey A Bailey
- Department of Pathology and Laboratory Medicine, Brown University, Providence, Rhode Island, USA
| | | | - Michael Emch
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, USA
- Carolina Population Center, University of North Carolina, Chapel Hill, North Carolina, USA
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Abstract
RTS,S/AS01 (Mosquirix®) is a vaccine against malaria caused by Plasmodium falciparum. In a phase 3 trial, RTS,S/AS01 showed vaccine efficacy against clinical malaria, severe malaria and malaria hospitalization, with an acceptable safety and tolerability profile, in children aged 6 weeks to 17 months; the vaccine efficacy was greater in children than in infants and waned over time. In another phase 3 trial, RTS,S/AS01 was noninferior to seasonal malaria chemoprevention in children. WHO recommends a 4-dose schedule of RTS,S/AS01 for the prevention of P. falciparum malaria in children from 5 months of age living in regions with moderate to high malaria transmission, with an optional 5-dose schedule for areas with highly seasonal malaria transmission. First results from large pilot implementation in Africa show that RTS,S/AS01 has a favourable safety profile, increases equity in access to malaria prevention, is highly cost effective, can be delivered through routine national immunization programmes and substantially reduces severe malaria burden. Malaria is a life-threatening disease caused by Plasmodium parasites, which are spread to humans through bites of infected mosquitoes. RTS,S/AS01 (Mosquirix®) is a vaccine against malaria caused by P. falciparum. In phase 3 trials, RTS,S/AS01 showed vaccine efficacy against P. falciparum malaria and was at least as effective as seasonal malaria chemoprevention in children, with an acceptable safety and tolerability profile. Results of the first 2 years of a large scale pilot implementation of RTS,S/AS01 in Africa allowed WHO to recommend the vaccine for the prevention of P. falciparum malaria in children from 5 months of age living in regions with moderate to high malaria transmission, with an optional use for seasonal malaria.
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Mistry A, Odwar B, Olewe F, Kurtis J, Moormann AM, Ong’echa JM. Pediatric Participant Retention Rates in a Longitudinal Malaria Immunology Study. Am J Trop Med Hyg 2022; 106:tpmd211052. [PMID: 35436763 PMCID: PMC9209909 DOI: 10.4269/ajtmh.21-1052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 12/20/2021] [Indexed: 11/16/2022] Open
Abstract
The resurgence of drug-resistant Plasmodium falciparum parasites continues to motivate the development of a safe and efficacious malaria vaccine. Immuno-epidemiologic studies of naturally acquired immunity (NAI) have been a useful strategy to identify new malaria vaccine targets. However, retention of pediatric participants throughout longitudinal studies is essential for gathering comprehensive exposure and outcome data. Within the context of a 3-year cohort (N = 400) study involving monthly finger prick and bi-annual venous blood sample collections, we conducted qualitative surveys to assess factors impacting participant retention. Phase 1 was conducted 3 months after enrollment in July 2018 and phase 2, 12 months later. In phase 1, 236 parents/guardians participated in focus groups and three withdrawn participants and 10 community health volunteers (CHVs) in key informant interviews. Qualitative analysis indicated overall satisfaction with the study, with 61.8% (136/220 respondents) reporting no concerns. Focus group discussants associated attendance with benefits such as improved access to comprehensive healthcare services. Community health volunteers reported concerns over village rumors of inappropriate use of blood samples and dangers associated with venous blood draws. Phase 2 involved 205 parents/guardians and revealed continued satisfaction, with 46.3% (95/205) identifying no concerns, but expressed increasing worries regarding the amount of venous blood sample. This concern was reflected in an uptick of missed visits when venous blood samples were scheduled. Future studies will address parental concerns to determine whether community engagement and education measures increase study retention until completion.
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Affiliation(s)
- Anushay Mistry
- University of Massachusetts Chan Medical School, Worcester, Massachusetts
| | - Boaz Odwar
- Kenya Medical Research Institute, Kisumu, Kenya
| | | | | | - Ann M. Moormann
- University of Massachusetts Chan Medical School, Worcester, Massachusetts
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Unwin HJT, Mwandigha L, Winskill P, Ghani AC, Hogan AB. Analysis of the potential for a malaria vaccine to reduce gaps in malaria intervention coverage. Malar J 2021; 20:438. [PMID: 34789253 PMCID: PMC8597213 DOI: 10.1186/s12936-021-03966-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 10/27/2021] [Indexed: 11/10/2022] Open
Abstract
Background The RTS,S/AS01 malaria vaccine is currently being evaluated in a cluster-randomized pilot implementation programme in three African countries. This study seeks to identify whether vaccination could reach additional children who are at risk from malaria but do not currently have access to, or use, core malaria interventions. Methods Using data from household surveys, the overlap between malaria intervention coverage and childhood vaccination (diphtheria-tetanus-pertussis dose 3, DTP3) uptake in 20 African countries with at least one first administrative level unit with Plasmodium falciparum parasite prevalence greater than 10% was calculated. Multilevel logistic regression was used to explore patterns of overlap by demographic and socioeconomic variables. The public health impact of delivering RTS,S/AS01 to those children who do not use an insecticide-treated net (ITN), but who received the DTP3 vaccine, was also estimated. Results Uptake of DTP3 was higher than malaria intervention coverage in most countries. Overall, 34% of children did not use ITNs and received DTP3, while 35% of children used ITNs and received DTP3, although this breakdown varied by country. It was estimated that there are 33 million children in these 20 countries who do not use an ITN. Of these, 23 million (70%) received the DTP3 vaccine. Vaccinating those 23 million children who receive DTP3 but do not use an ITN could avert up to an estimated 9.7 million (range 8.5–10.8 million) clinical malaria cases each year, assuming all children who receive DTP3 are administered all four RTS,S doses. An additional 10.8 million (9.5–12.0 million) cases could be averted by vaccinating those 24 million children who receive the DTP3 vaccine and use an ITN. Children who had access to or used an ITN were 9–13% more likely to reside in rural areas compared to those who had neither intervention regardless of vaccination status. Mothers’ education status was a strong predictor of intervention uptake and was positively associated with use of ITNs and vaccination uptake and negatively associated with having access to an ITN but not using it. Wealth was also a strong predictor of intervention coverage. Conclusions Childhood vaccination to prevent malaria has the potential to reduce inequity in access to existing malaria interventions and could substantially reduce the childhood malaria burden in sub-Saharan Africa, even in regions with lower existing DTP3 coverage. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03966-x.
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Affiliation(s)
- H Juliette T Unwin
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London, W2 1PG, UK
| | - Lazaro Mwandigha
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London, W2 1PG, UK.,Nuffield Department of Primary Care Health Sciences, University of Oxford Radcliffe Observatory Quarter, Woodstock Road, Oxford, OX2 6GG, UK
| | - Peter Winskill
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London, W2 1PG, UK
| | - Azra C Ghani
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London, W2 1PG, UK
| | - Alexandra B Hogan
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London, W2 1PG, UK.
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Bell GJ, Agnandji ST, Asante KP, Ghansah A, Kamthunzi P, Emch M, Bailey JA. Impacts of Ecology, Parasite Antigenic Variation, and Human Genetics on RTS,S/AS01e Malaria Vaccine Efficacy. CURR EPIDEMIOL REP 2021; 8:79-88. [PMID: 34367877 PMCID: PMC8324449 DOI: 10.1007/s40471-021-00271-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2021] [Indexed: 02/07/2023]
Abstract
PURPOSE OF REVIEW Global malaria elimination has little chance of success without an effective vaccine. The first malaria vaccine, RTS,S/AS01e, demonstrated moderate efficacy against clinical malaria in phase III trials and is undergoing large-scale effectiveness trials in Africa. Importantly, the vaccine did not perform equally well between phase III study sites. Though reasons for the moderate efficacy and this variation are unclear, various mechanisms have been suggested. This review summarizes the recent literature on such mechanisms, with a focus on those involving landscape ecology, parasite antigenic variation, and human host genetic differences. RECENT FINDINGS Transmission intensity may have a role pre- and post-vaccination in modulating immune responses to the vaccine. Furthermore, malaria incidence may "rebound" in vaccinated populations living in high transmission intensity settings. There is growing evidence that both genetic variation in the parasite circumsporozoite protein and variation of human host genetic factors affect RTS,S vaccine efficacy. These genetic factors may be interacting in complex ways to produce variation in the natural and vaccine-induced immune responses that protect against malaria. SUMMARY Due to the modest efficacy of RTS,S/AS01e, the combinations of factors (ecological, parasite, human host) impacting its effectiveness must be clearly understood, as this information will be critical for implementation policy and future vaccine designs.
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Affiliation(s)
- Griffin J. Bell
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599 USA
| | - Selidji Todagbe Agnandji
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon ,Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany
| | | | - Anita Ghansah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | | | - Michael Emch
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599 USA ,Department of Geography, University of North Carolina, Chapel Hill 220 E Cameron Ave, Chapel Hill, NC 27599 USA
| | - Jeffrey A. Bailey
- Department of Pathology and Laboratory Medicine, Brown University, 55 Claverick St, Rm 314B, Providence, RI 02912 USA
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10
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Bell GJ, Loop MS, Mvalo T, Juliano JJ, Mofolo I, Kamthunzi P, Tegha G, Lievens M, Bailey J, Emch M, Hoffman I. Environmental modifiers of RTS,S/AS01 malaria vaccine efficacy in Lilongwe, Malawi. BMC Public Health 2020; 20:910. [PMID: 32532234 PMCID: PMC7291743 DOI: 10.1186/s12889-020-09039-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 06/03/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND RTS,S/AS01 is the first vaccine against malaria to undergo pilot implementation, beginning in 2019 and vaccinating 360,000 children per year in Malawi, Ghana, and Kenya. The four-dose vaccine is given as a primary three-dose series with a fourth dose given approximately 18 months later. The efficacy of RTS,S/AS01 was variable among the 11 sites participating in the 2009-2014 phase III trial (MALARIA-055, NCT00866619), possibly due to differences in transmission intensity. However, a within-site examination of environmental factors related to transmission intensity and their impact on vaccine efficacy has yet to be conducted. METHODS We implemented the phase III RTS,S/AS01 trial at the Malawi site, which enrolled 1578 infants (6-12 weeks) and children (5-17 months) living in the Lilongwe District in Central Malawi and followed them for 3 years between 2009 and 2014. A global positioning system survey and an ecological questionnaire were conducted to collect participant household locations and characteristics, while additional data on background malaria prevalence were obtained from a concurrent Malaria Transmission Intensity (MTI) survey. Negative binomial regression models were used to assess whether the efficacy of the vaccine varied by estimated background malaria prevalence, household roof type, or amount of nearby vegetation. RESULTS Vaccine efficacy did not significantly vary by estimated malaria prevalence or by roof type. However, increased vegetation cover was associated with an increase in the efficacy of the three-dose primary RTS,S/AS01 series in the 18 months before the fourth dose and a decrease in the efficacy of the primary vaccine series in the second 18 months following, if the fourth dose was not given. Vegetation cover did not alter the efficacy of the fourth dose in a statistically or practically significant manner. CONCLUSIONS Vegetation coverage in this study site might be a proxy for nearness to rivers or branching, shallow wetlands called "dambos" which could serve as breeding sites for mosquitoes. We observed statistically significant modification of the efficacy of RTS,S/AS01 by forest cover, suggesting that initial vaccine efficacy and the importance of the fourth dose varies based on ecological context. TRIAL REGISTRATION Efficacy of GSK Biologicals' Candidate Malaria Vaccine (257049) Against Malaria Disease Caused by P. falciparum Infection in Infants and Children in Africa. NCT00866619 prospectively registered 20 March 2009.
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Affiliation(s)
- Griffin J. Bell
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599 USA
| | - Matthew S. Loop
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599 USA
| | - Tisungane Mvalo
- University of North Carolina, Chapel Hill, NC 27599 USA
- University of North Carolina Project Malawi, Lilongwe, Malawi
| | - Jonathan J. Juliano
- Division of Infectious Diseases, School of Medicine, University of North Carolina, Chapel Hill, NC 27599 USA
| | - Innocent Mofolo
- University of North Carolina, Chapel Hill, NC 27599 USA
- University of North Carolina Project Malawi, Lilongwe, Malawi
| | - Portia Kamthunzi
- University of North Carolina, Chapel Hill, NC 27599 USA
- University of North Carolina Project Malawi, Lilongwe, Malawi
| | - Gerald Tegha
- University of North Carolina Project Malawi, Lilongwe, Malawi
| | | | - Jeffrey Bailey
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI 02912 USA
| | - Michael Emch
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599 USA
| | - Irving Hoffman
- University of North Carolina, Chapel Hill, NC 27599 USA
- University of North Carolina Project Malawi, Lilongwe, Malawi
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