Publications
109 results found
Ainslie KEC, Walters CE, Fu H, et al., 2020, Evidence of initial success for China exiting COVID-19 social distancing policy after achieving containment [version 1; peer review: 2 approved], Wellcome Open Res, Vol: 5, ISSN: 2398-502X
Background: The COVID-19 epidemic was declared a Global Pandemic by WHO on 11 March 2020. By 24 March 2020, over 440,000 cases and almost 20,000 deaths had been reported worldwide. In response to the fast-growing epidemic, which began in the Chinese city of Wuhan, Hubei, China imposed strict social distancing in Wuhan on 23 January 2020 followed closely by similar measures in other provinces. These interventions have impacted economic productivity in China, and the ability of the Chinese economy to resume without restarting the epidemic was not clear. Methods: Using daily reported cases from mainland China and Hong Kong SAR, we estimated transmissibility over time and compared it to daily within-city movement, as a proxy for economic activity. Results: Initially, within-city movement and transmission were very strongly correlated in the five mainland provinces most affected by the epidemic and Beijing. However, that correlation decreased rapidly after the initial sharp fall in transmissibility. In general, towards the end of the study period, the correlation was no longer apparent, despite substantial increases in within-city movement. A similar analysis for Hong Kong shows that intermediate levels of local activity were maintained while avoiding a large outbreak. At the very end of the study period, when China began to experience the re-introduction of a small number of cases from Europe and the United States, there is an apparent up-tick in transmission. Conclusions: Although these results do not preclude future substantial increases in incidence, they suggest that after very intense social distancing (which resulted in containment), China successfully exited its lockdown to some degree. Elsewhere, movement data are being used as proxies for economic activity to assess the impact of interventions. The results presented here illustrate how the eventual decorrelation between transmission and movement is likely a key feature of successful COVID-19 exit strategies.
Grassly N, Pons Salort M, Parker E, et al., 2020, Report 16: Role of testing in COVID-19 control
The World Health Organization has called for increased molecular testing in response to the COVID-19 pandemic, but different countries have taken very different approaches. We used a simple mathematical model to investigate the potential effectiveness of alternative testing strategies for COVID-19 control. Weekly screening of healthcare workers (HCWs) and other at-risk groups using PCR or point-of-care tests for infection irrespective of symptoms is estimated to reduce their contribution to transmission by 25-33%, on top of reductions achieved by self-isolation following symptoms. Widespread PCR testing in the general population is unlikely to limit transmission more than contact-tracing and quarantine based on symptoms alone, but could allow earlier release of contacts from quarantine. Immunity passports based on tests for antibody or infection could support return to work but face significant technical, legal and ethical challenges. Testing is essential for pandemic surveillance but its direct contribution to the prevention of transmission is likely to be limited to patients, HCWs and other high-risk groups.
Slater HC, Foy BD, Kobylinski K, et al., 2020, Ivermectin as a novel complementary malaria control tool to reduce incidence and prevalence: a modelling study, Lancet Infectious Diseases, Vol: 20, Pages: 498-508, ISSN: 1473-3099
BACKGROUND: Ivermectin is a potential new vector control tool to reduce malaria transmission. Mosquitoes feeding on a bloodmeal containing ivermectin have a reduced lifespan, meaning they are less likely to live long enough to complete sporogony and become infectious. We aimed to estimate the effect of ivermectin on malaria transmission in various scenarios of use. METHODS: We validated an existing population-level mathematical model of the effect of ivermectin mass drug administration (MDA) on the mosquito population and malaria transmission against two datasets: clinical data from a cluster- randomised trial done in Burkina Faso in 2015 wherein ivermectin was given to individuals taller than 90 cm and entomological data from a study of mosquito outcomes after ivermectin MDA for onchocerciasis or lymphatic filariasis in Burkina Faso, Senegal, and Liberia between 2008 and 2013. We extended the existing model to include a range of complementary malaria interventions (seasonal malaria chemoprevention and MDA with dihydroartemisinin-piperaquine) and to incorporate new data on higher doses of ivermectin with a longer mosquitocidal effect. We consider two ivermectin regimens: a single dose of 400 μg/kg (1 × 400 μg/kg) and three consecutive daily doses of 300 μg/kg per day (3 × 300 μg/kg). We simulated the effect of these two doses in a range of usage scenarios in different transmission settings (highly seasonal, seasonal, and perennial). We report percentage reductions in clinical incidence and slide prevalence. FINDINGS: We estimate that MDA with ivermectin will reduce prevalence and incidence and is most effective in areas with highly seasonal transmission. In a highly seasonal moderate transmission setting, three rounds of ivermectin only MDA at 3 × 300 μg/kg (rounds spaced 1 month apart) and 70% coverage is predicted to reduce clinical incidence by 71% and prevalence by 34%. We predict that adding ivermectin MDA to seasonal malaria ch
Ainslie K, Walters C, Fu H, et al., 2020, Report 11: Evidence of initial success for China exiting COVID-19 social distancing policy after achieving containment
The COVID-19 epidemic was declared a Global Pandemic by WHO on 11 March 2020. As of 20 March 2020, over 254,000 cases and 10,000 deaths had been reported worldwide. The outbreak began in the Chinese city of Wuhan in December 2019. In response to the fast-growing epidemic, China imposed strict social distancing in Wuhan on 23 January 2020 followed closely by similar measures in other provinces. At the peak of the outbreak in China (early February), there were between 2,000 and 4,000 new confirmed cases per day. For the first time since the outbreak began there have been no new confirmed cases caused by local transmission in China reported for five consecutive days up to 23 March 2020. This is an indication that the social distancing measures enacted in China have led to control of COVID-19 in China. These interventions have also impacted economic productivity in China, and the ability of the Chinese economy to resume without restarting the epidemic is not yet clear. Here, we estimate transmissibility from reported cases and compare those estimates with daily data on within-city movement, as a proxy for economic activity. Initially, within-city movement and transmission were very strongly correlated in the 5 provinces most affected by the epidemic and Beijing. However, that correlation is no longer apparent even though within-city movement has started to increase. A similar analysis for Hong Kong shows that intermediate levels of local activity can be maintained while avoiding a large outbreak. These results do not preclude future epidemics in China, nor do they allow us to estimate the maximum proportion of previous within-city activity that will be recovered in the medium term. However, they do suggest that after very intense social distancing which resulted in containment, China has successfully exited their stringent social distancing policy to some degree. Globally, China is at a more advanced stage of the pandemic. Policies implemented to reduce the spread of CO
Ferguson N, Laydon D, Nedjati Gilani G, et al., 2020, Report 9: Impact of non-pharmaceutical interventions (NPIs) to reduce COVID19 mortality and healthcare demand
The global impact of COVID-19 has been profound, and the public health threat it represents is the most serious seen in a respiratory virus since the 1918 H1N1 influenza pandemic. Here we present the results of epidemiological modelling which has informed policymaking in the UK and other countries in recent weeks. In the absence of a COVID-19 vaccine, we assess the potential role of a number of public health measures – so-called non-pharmaceutical interventions (NPIs) – aimed at reducing contact rates in the population and thereby reducing transmission of the virus. In the results presented here, we apply a previously published microsimulation model to two countries: the UK (Great Britain specifically) and the US. We conclude that the effectiveness of any one intervention in isolation is likely to be limited, requiring multiple interventions to be combined to have a substantial impact on transmission. Two fundamental strategies are possible: (a) mitigation, which focuses on slowing but not necessarily stopping epidemic spread – reducing peak healthcare demand while protecting those most at risk of severe disease from infection, and (b) suppression, which aims to reverse epidemic growth, reducing case numbers to low levels and maintaining that situation indefinitely. Each policy has major challenges. We find that that optimal mitigation policies (combining home isolation of suspect cases, home quarantine of those living in the same household as suspect cases, and social distancing of the elderly and others at most risk of severe disease) might reduce peak healthcare demand by 2/3 and deaths by half. However, the resulting mitigated epidemic would still likely result in hundreds of thousands of deaths and health systems (most notably intensive care units) being overwhelmed many times over. For countries able to achieve it, this leaves suppression as the preferred policy option. We show that in the UK and US context, suppression will minimally requi
Gaythorpe K, Imai N, Cuomo-Dannenburg G, et al., 2020, Report 8: Symptom progression of COVID-19
The COVID-19 epidemic was declared a Public Health Emergency of International Concern (PHEIC) by WHO on 30th January 2020 [1]. As of 8 March 2020, over 107,000 cases had been reported. Here, we use published and preprint studies of clinical characteristics of cases in mainland China as well as case studies of individuals from Hong Kong, Japan, Singapore and South Korea to examine the proportional occurrence of symptoms and the progression of symptoms through time.We find that in mainland China, where specific symptoms or disease presentation are reported, pneumonia is the most frequently mentioned, see figure 1. We found a more varied spectrum of severity in cases outside mainland China. In Hong Kong, Japan, Singapore and South Korea, fever was the most frequently reported symptom. In this latter group, presentation with pneumonia is not reported as frequently although it is more common in individuals over 60 years old. The average time from reported onset of first symptoms to the occurrence of specific symptoms or disease presentation, such as pneumonia or the use of mechanical ventilation, varied substantially. The average time to presentation with pneumonia is 5.88 days, and may be linked to testing at hospitalisation; fever is often reported at onset (where the mean time to develop fever is 0.77 days).
Kitojo C, Gutman JR, Chacky F, et al., 2019, Estimating malaria burden among pregnant women using data from antenatal care centres in Tanzania: a population-based study, The Lancet Global Health, Vol: 7, Pages: e1695-e1705, ISSN: 2214-109X
BACKGROUND: More timely estimates of malaria prevalence are needed to inform optimal control strategies and measure progress. Since 2014, Tanzania has implemented nationwide malaria screening for all pregnant women within the antenatal care system. We aimed to compare malaria test results during antenatal care to two population-based prevalence surveys in Tanzanian children aged 6-59 months to examine their potential in measuring malaria trends and progress towards elimination. METHODS: Malaria test results from pregnant women screened at their first antenatal care visits at health-care facilities (private and public) in all 184 districts of Tanzania between Jan 1, 2014, and Dec 31, 2017, were collected from the Health Management Information Systems and District Health Information System 2. We excluded facilities with no recorded antenatal care attendees during the time period. We standardised results to account for testing uptake and weighted them by the timing of two population-based surveys of childhood malaria prevalence done in 2015-16 (Demographic and Health Survey) and 2017 (Malaria Indicator Survey). We assessed regional-level correlation using Spearman's coefficient and assessed the consistency of monthly district-level prevalence ranking using Kendall's correlation coefficient. FINDINGS: Correlation between malaria prevalence at antenatal care and among children younger than 5 years was high (r≥0·83 for both surveys), although declines in prevalence at antenatal care were generally smaller than among children. Consistent heterogeneity (p<0·05) in antenatal care prevalence at the district level was evident in all but one region (Kilimanjaro). Data from antenatal care showed declining prevalence in three regions (Arusha, Kilimanjaro, and Manyara) where surveys estimated zero prevalence. INTERPRETATION: Routine antenatal care-based screening can be used to assess heterogeneity in transmission at finer resolution than population-based surve
Mayor A, Menendez C, Walker PGT, 2019, Targeting pregnant women for malaria surveillance, Trends in Parasitology, Vol: 35, Pages: 677-686, ISSN: 0169-4758
Women attending antenatal care (ANC) are a generally healthy, easy-access population, contributing valuable data for infectious disease surveillance at the community level. ANC-based malaria surveillance would provide a routine measure of the malaria burden in pregnancy, which countries lack, whilst potentially improving pregnancy outcomes. It could also offer contemporary information on temporal trends and the geographic distribution of malaria burden as well as intervention coverage in the population to guide resource allocation and to assess progress towards elimination. Here, we review the factors underlying the relationship between Plasmodium falciparum in pregnancy and in the community, and outline strengths and limitations of an ANC-based surveillance in sub-Saharan Africa, its potential role within wider malaria surveillance systems, and subsequent programmatic applications.
Winskill P, Walker PG, Cibulskis RE, et al., 2019, Prioritizing the scale-up of interventions for malaria control and elimination, Malaria Journal, Vol: 18, ISSN: 1475-2875
BackgroundA core set of intervention and treatment options are recommended by the World Health Organization for use against falciparum malaria. These are treatment, long-lasting insecticide-treated bed nets, indoor residual spraying, and chemoprevention options. Both domestic and foreign aid funding for these tools is limited. When faced with budget restrictions, the introduction and scale-up of intervention and treatment options must be prioritized.MethodsEstimates of the cost and impact of different interventions were combined with a mathematical model of malaria transmission to estimate the most cost-effective prioritization of interventions. The incremental cost effectiveness ratio was used to select between scaling coverage of current interventions or the introduction of an additional intervention tool.ResultsPrevention, in the form of vector control, is highly cost effective and scale-up is prioritized in all scenarios. Prevention reduces malaria burden and therefore allows treatment to be implemented in a more cost-effective manner by reducing the strain on the health system. The chemoprevention measures (seasonal malaria chemoprevention and intermittent preventive treatment in infants) are additional tools that, provided sufficient funding, are implemented alongside treatment scale-up. Future tools, such as RTS,S vaccine, have impact in areas of higher transmission but were introduced later than core interventions.ConclusionsIn a programme that is budget restricted, it is essential that investment in available tools be effectively prioritized to maximize impact for a given investment. The cornerstones of malaria control: vector control and treatment, remain vital, but questions of when to scale and when to introduce other interventions must be rigorously assessed. This quantitative analysis considers the scale-up or core interventions to inform decision making in this area.
Winskill P, Walker P, Cibulskis R, et al., 2019, Prioritizing the scale up of interventions for malaria control and elimination, Malaria Journal, ISSN: 1475-2875
Cuomo-Dannenburg GM, Walker P, Verity R, et al., 2019, IMPLICATION OF SULFADOXINE-PYRIMETHAMINE RESISTANCE-ASSOCIATED MUTATIONS ON THE PROTECTIVE EFFICACY OF SEASONAL MALARIA CHEMOPREVENTION: A PHARMACOKINETIC-PHARMACODYNAMIC ANALYSIS, 68th Annual Meeting of the American-Society-for-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 189-189, ISSN: 0002-9637
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Samuels AM, Towett O, Seda B, et al., 2019, DIAGNOSTIC PERFORMANCE OF ULTRA-SENSITIVE RAPID DIAGNOSTIC TESTS FOR MALARIA IN PREGNANT WOMEN ATTENDING ANTENATAL CLINICS IN WESTERN KENYA, 68th Annual Meeting of the American-Society-for-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 276-276, ISSN: 0002-9637
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Hellewell J, Walker P, Ghani A, et al., 2018, Using ante-natal clinic prevalence data to monitor temporal changes in malaria incidence in a humanitarian setting in the Democratic Republic of Congo, Malaria Journal, Vol: 17, ISSN: 1475-2875
BackgroundThe number of clinical cases of malaria is often recorded in resource constrained or conflict settings as a proxy for disease burden. Interpreting case count data in areas of humanitarian need is challenging due to uncertainties in population size caused by security concerns, resource constraints and population movement. Malaria prevalence in women visiting ante-natal care (ANC) clinics has the potential to be an easier and more accurate metric for malaria surveillance that is unbiased by population size if malaria testing is routinely conducted irrespective of symptoms. MethodsA suite of distributed lag non-linear models was fitted to clinical incidence time-series data in children under 5 years and ANC prevalence data from health centres run by Médecins Sans Frontières in the Democratic Republic of Congo, which implement routine intermittent screening and treatment (IST) alongside intermittent preventative treatment in pregnancy (IPTp). These statistical models enable the temporal relationship between the two metrics to be disentangled. ResultsThere was a strong relationship between the ANC prevalence and clinical incidence suggesting that both can be used to describe current malaria endemicity. There was no evidence that ANC prevalence could predict future clinical incidence, though a change in clinical incidence was shown to influence ANC prevalence up to 3 months into the future. ConclusionsThe results indicate that ANC prevalence may be a suitable metric for retrospective evaluations of the impact of malaria interventions and is a useful method for evaluating long-term malaria trends in resource constrained settings.
White MT, Walker PGT, Karl S, et al., 2018, Mathematical modelling of the impact of expanding levels of malaria control interventions on Plasmodium vivax, Nature Communications, Vol: 9, ISSN: 2041-1723
Plasmodium vivax poses unique challenges for malaria control and elimination, notably the potential for relapses to maintain transmission in the face of drug-based treatment and vector control strategies. We developed an individual-based mathematical model of P. vivax transmission calibrated to epidemiological data from Papua New Guinea (PNG). In many settings in PNG, increasing bed net coverage is predicted to reduce transmission to less than 0.1% prevalence by light microscopy, however there is substantial risk of rebounds in transmission if interventions are removed prematurely. In several high transmission settings, model simulations predict that combinations of existing interventions are not sufficient to interrupt P. vivax transmission. This analysis highlights the potential options for the future of P. vivax control: maintaining existing public health gains by keeping transmission suppressed through indefinite distribution of interventions; or continued development of strategies based on existing and new interventions to push for further reduction and towards elimination.
Routledge I, Chevez JER, Cucunubá ZM, et al., 2018, Estimating spatiotemporally varying malaria reproduction numbers in a near elimination setting, Nature Communications, Vol: 9, Pages: 1-8, ISSN: 2041-1723
In 2016 the World Health Organization identified 21 countries that could eliminate malaria by 2020. Monitoring progress towards this goal requires tracking ongoing transmission. Here we develop methods that estimate individual reproduction numbers and their variation through time and space. Individual reproduction numbers, Rc, describe the state of transmission at a point in time and differ from mean reproduction numbers, which are averages of the number of people infected by a typical case. We assess elimination progress in El Salvador using data for confirmed cases of malaria from 2010 to 2016. Our results demonstrate that whilst the average number of secondary malaria cases was below one (0.61, 95% CI 0.55–0.65), individual reproduction numbers often exceeded one. We estimate a decline in Rc between 2010 and 2016. However we also show that if importation is maintained at the same rate, the country may not achieve malaria elimination by 2020.
Desai M, Hill J, Fernandes S, et al., 2018, Prevention of malaria in pregnancy, Obstetrical and Gynecological Survey, Vol: 73, Pages: 342-344, ISSN: 0029-7828
© 2018 Wolters Kluwer Health, Inc. All rights reserved. Although the World Health Organization (WHO) has established recommendations for prevention of malaria, it remains one of the most preventable causes of adverse birth outcomes. The WHO recommends intermittent preventive treatment in pregnancy (IPTp) with for women who are HIV-negative, or co-trimoxazole prophylaxis for women who are HIV-positive. However, parasite resistance to sulfadoxine pyrimethamine in sub-Saharan Africa has led researchers to pursue other screen-and-treat approaches. This analysis reviews the effect of sulfadoxine-pyrimethamine on IPTp efficacy and summarizes trials focused on the prevention of malaria in pregnancy in areas where malaria is endemic. A total of 65 efficacy-related articles were included. Sulfadoxine-pyrimethamine as IPTp in pregnant women reduces the risk of comorbidities including anemia, antenatal and placental parasitemia, spontaneous abortions, and low birthweight. Reviews of this regimen have found it to be highly costeffective when combined with existing antenatal services. A meta-analysis conducted in Africa found that 3-course or monthly IPTp with sulfadoxine-pyrimethamine was much more effective in reducing adverse birth outcomes than the standard 2-course regimen, leading the WHO to update its guidelines in 2012. Observational studies have shown that resistance to sulfadoxine-pyrimethamine reduces the parasitological efficacy of IPTp and duration of prophylaxis. High resistance is found in regions where prevalence of parasites with quintuple Plasmodium falciparum dihydrofolate reductase (Pfdhfr) and dihydropteroate synthetase (Pfdhps) mutations is greater than 90%. Even in such locations, sulfadoxine-pyrimethamine regimens continue to have beneficial effects on low birthweight. Research into alternative IPTp therapies are ongoing, yet many proposed alternatives thus far have found that they are tolerated poorly by patients. Two trials of IPTp using dihydroart
Desai M, Hill J, Fernandes S, et al., 2018, Prevention of malaria in pregnancy., Lancet Infectious Diseases, ISSN: 1473-3099
Malaria remains one of the most preventable causes of adverse birth outcomes. Intermittent preventive treatment in pregnancy (IPTp) with sulfadoxine-pyrimethamine is used to prevent malaria, but resistance to this drug combination has decreased its efficacy and new alternatives are needed. In Africa, a meta-analysis showed three-course or monthly IPTp with sulfadoxine-pyrimethamine to be safe and more effective than the original two-course sulfadoxine-pyrimethamine strategy, prompting WHO to update its policy in 2012. Although resistance to sulfadoxine-pyrimethamine reduces the parasitological efficacy of IPTp, this drug combination remains associated with reduced incidence of low birthweight in areas where prevalence of parasites with quintuple Plasmodium falciparum dihydrofolate reductase (Pfdhfr) and dihydropteroate synthetase (Pfdhps) mutations is greater than 90%. Nevertheless, its effectiveness is compromised in women infected with sextuple mutant parasites. Six trials of IPTp showed that neither amodiaquine, mefloquine, nor chloroquine-azithromycin are suitable replacements for sulfadoxine-pyrimethamine because of poor tolerability. Furthermore, four trials showed that intermittent screening and treatment with the current generation of malaria rapid diagnostic tests was not a suitable alternative strategy to IPTp with sulfadoxine-pyrimethamine, even in areas with high prevalence of quintuple mutations. Two trials showed that IPTp with dihydroartemisinin-piperaquine was well tolerated, effective, and acceptable for IPTp, with monthly regimens being the most effective. Coverage of IPTp and insecticide-treated nets continues to lag behind targets. The key barriers to uptake are well documented, and many are open to intervention. Outside of Africa, a single trial suggests a potential role for integrated approaches that combine sulfadoxine-pyrimethamine with azithromycin for IPTp in areas of Papua New Guinea where malaria transmission is high. Modelling analysis s
Slater H, Li R, Walker P, et al., 2018, MODELLING THE IMPACT OF AN ULTRA-SENSITIVE <it>PLASMODIUM FALCIPARUM</it> RAPID DIAGNOSTIC TEST (U-RDT): DETECTING ASYMPTOMATIC INFECTIONS AND THE POTENTIAL FOR OVERTREATMENT, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 540-541, ISSN: 0002-9637
Thindwa D, Walker P, Terlouw A, et al., 2018, MODELLING THE POTENTIAL IMPACT ON SPREAD OF ARTEMISININ AND PARTNER-DRUG RESISTANCE OF INTERMITTENT PREVENTIVE THERAPY OF MALARIA IN PREGNANCY, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 340-340, ISSN: 0002-9637
Li R, Ghani A, Walker P, et al., 2018, MODELING HRP2 DYNAMICS AND THE IMPLICATIONS FOR A NEW ULTRA-SENSITIVE RAPID DIAGNOSTIC TEST (U-RDT), 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 539-539, ISSN: 0002-9637
Berry I, Walker P, Tagbor H, et al., 2017, Seasonal Dynamics of Malaria in Pregnancy in West Africa: Evidence for Carriage of Infections Acquired Before Pregnancy Until First Contact with Antenatal Care., American Journal of Tropical Medicine and Hygiene, Vol: 98, Pages: 534-542, ISSN: 0002-9637
In malaria-endemic areas, Plasmodium falciparum prevalence is often high in young women because of 1) low use of insecticide-treated nets before their first pregnancy and 2) acquired immunity, meaning infections are asymptomatic and thus untreated. Consequently, a common source of malaria in pregnancy (MiP) may be infected women becoming pregnant, rather than pregnant women becoming infected. In this study, prevalence of infection was determined by microscopy at first antenatal care (ANC) visit in primigravidae and secundigravidae in Ghana, Burkina Faso, Mali, and The Gambia, four countries with strong seasonal variations in transmission. Duration of pregnancy spent in the rainy season and other risk factors for infection were evaluated using multivariable Poisson regression. We found that the overall prevalence of malaria at first ANC was generally high and increased with time spent pregnant during the rainy season: prevalence among those with the longest exposure was 59.7% in Ghana, 56.7% in Burkina Faso, 42.2% in Mali, and 16.8% in Gambia. However, the prevalence was substantial even among women whose entire pregnancy before first ANC had occurred in the dry season: 41.3%, 34.4%, 11.5%, and 7.8%, respectively, in the four countries. In multivariable analysis, risk of infection was also higher among primigravidae, younger women, and those of lower socioeconomic status, independent of seasonality. High prevalence among women without exposure to high transmission during their pregnancy suggests that part of the MiP burden results from long-duration infections, including those acquired preconception. Prevention of malaria before pregnancy is needed to reduce the MiP burden.
Brady O, Finn T, Hay SI, et al., 2017, malERA: An updated research agenda for combination interventions and modelling in malaria elimination and eradication, PLoS Medicine, Vol: 14, ISSN: 1549-1277
This paper summarises key advances and priorities since the 2011 presentation of theMalaria Eradication Research Agenda (malERA), with a focus on the combinations of interventiontools and strategies for elimination and their evaluation using modelling approaches.With an increasing number of countries embarking on malaria elimination programmes,national and local decisions to select combinations of tools and deployment strategiesdirected at malaria elimination must address rapidly changing transmission patterns acrossdiverse geographic areas. However, not all of these approaches can be systematically evaluatedin the field. Thus, there is potential for modelling to investigate appropriate ‘packages’of combined interventions that include various forms of vector control, case management,surveillance, and population-based approaches for different settings, particularly at lowertransmission levels. Modelling can help prioritise which intervention packages should betested in field studies, suggest which intervention package should be used at a particularlevel or stratum of transmission intensity, estimate the risk of resurgence when scaling downspecific interventions after local transmission is interrupted, and evaluate the risk and impactof parasite drug resistance and vector insecticide resistance. However, modelling interventionpackage deployment against a heterogeneous transmission background is a challenge.Further validation of malaria models should be pursued through an iterative process,whereby field data collected with the deployment of intervention packages is used to refinemodels and make them progressively more relevant for assessing and predicting eliminationoutcomes.
Winskill P, Slater H, Griffin J, et al., 2017, The US President's Malaria Initiative, Plasmodium falciparum transmission and mortality: A modelling study, PLoS Medicine, Vol: 14, ISSN: 1549-1277
BackgroundAlthough significant progress has been made in reducing malaria transmission globally inrecent years, a large number of people remain at risk and hence the gains made are fragile.Funding lags well behind amounts needed to protect all those at risk and ongoing contributionsfrom major donors, such as the President’s Malaria Initiative (PMI), are vital to maintainprogress and pursue further reductions in burden. We use a mathematical modellingapproach to estimate the impact of PMI investments to date in reducing malaria burden andto explore the potential negative impact on malaria burden should a proposed 44% reductionin PMI funding occur.Methods and findingsWe combined an established mathematical model of Plasmodium falciparum transmissiondynamics with epidemiological, intervention, and PMI-financing data to estimate the contributionPMI has made to malaria control via funding for long-lasting insecticide treated nets(LLINs), indoor residual spraying (IRS), and artemisinin combination therapies (ACTs). Weestimate that PMI has prevented 185 million (95% CrI: 138 million, 230 million) malariacases and saved 940,049 (95% CrI: 545,228, 1.4 million) lives since 2005. If funding is maintained,PMI-funded interventions are estimated to avert a further 162 million cases (95%CrI: 116 million, 194 million) cases, saving a further 692,589 (95% CrI: 392,694, 955,653)lives between 2017 and 2020. With an estimate of US$94 (95% CrI: US$51, US$166) perDisability Adjusted Life Year (DALY) averted, PMI-funded interventions are highly costeffective.We also demonstrate the further impact of this investment by reducing caseloadson health systems. If a 44% reduction in PMI funding were to occur, we predict that this lossof direct aid could result in an additional 67 million (95% CrI: 49 million, 82 million) cases and290,649 deaths (95% CrI: 167,208, 395,263) deaths between 2017 and 2020. We have notmodelled indirect impacts of PMI funding (such as health systems strengthening
Winskill P, Walker PG, Griffin JT, et al., 2017, OPTIMIZING THE GLOBAL ALLOCATION OF MALARIA FUNDS, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 117-117, ISSN: 0002-9637
Hamainza B, Mudenda M, Miller J, et al., 2017, ZAMBIA'S NATIONAL STRATEGY TO MOVE FROM ACCELERATED BURDEN REDUCTION TO MALARIA ELIMINATION BY 2020, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 486-486, ISSN: 0002-9637
Cairns M, Walker PG, Griffin JT, et al., 2017, OPTIMIZING SEASONAL MALARIA CHEMOPREVENTION (SMC) IN AFRICA: ESTIMATING THE IMPACT OF INCREASING THE NUMBER OF SMC CYCLES ON THE NUMBER OF CHILDREN PROTECTED, THE MALARIA BURDEN AND COST-EFFECTIVENESS, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 398-398, ISSN: 0002-9637
Goncalves BP, Walker PG, Cairns M, et al., 2017, Pregnant Women: An Overlooked Asset to Plasmodium falciparum Malaria Elimination Campaigns?, TRENDS IN PARASITOLOGY, Vol: 33, Pages: 510-518, ISSN: 1471-4922
Walker PGT, Floyd J, ter Kuile F, et al., 2017, Estimated Impact on Birth Weight of Scaling-up Intermittent Preventive Treatment for Malaria in Pregnancy Given Sulphadoxine-Pyrimethamine Resistance in Africa: a Mathematical Model, PLOS Medicine, Vol: 14, ISSN: 1549-1277
Background:Malaria transmission has declined substantially in the 21stcentury but pregnant women in areas of sustained transmission still require protection to prevent the adverse pregnancy and birth outcomes associated with malaria in pregnancy(MiP). A recent “Call to Action” has been issued to address the continuing low coverage of intermittent preventative treatment for malaria during pregnancy (IPTp). This call has, however, been questioned by some, in part due to concerns about resistance to sulphadoxine-pyrimethamine (SP), the only drug currently recommended for IPTp.Methods and Findings:Using an existing mathematical model of MiPwe combined estimates of the changing endemicity of malaria across Africa with maps of SPresistance mutationsand current coverage of antenatal access and IPTp-SPacross Africa. Using estimates of the relationship between these mutations and the parasitological efficacy of SP during pregnancy,we estimate the varying impact of IPTp-SP across Africaand the incremental value of enhancing IPTp-SP uptake to match current antenatal clinic (ANC)coverage. The risksof MiP andmalaria-attributable low birthweight (mLBW)in unprotected pregnancies(i.e. those not using insecticide treated nets (ITNs)) leading to live births fellby 37% (33%-41% 95% credible interval (crI))and 31% (27%-34%95% crI)respectively from 2000 to 2015across endemicareas insub-Saharan Africa. However, these gains are fragile, and coverage is far from optimal. In 2015,9.5(8.3-10.4 05% crI) million (m) of 30.6mpregnancies in theseareas would still have been infected with P. falciparum withoutintervention, leading to 750,000 (390,000-1.1m95% crI))malaria-attributable LBW deliveries. 6.6(5.6-7.3 95% crI) mof these 9.5m (69.3%)pregnanciesat risk ofinfection(and 53.4% [16.3m/30.6m] of allpregnancies)occurred in settings with near-perfect SP curative efficacy (>99%)based on the most recent estimates of resistance. 44%of thesepregnancies(23% of all pregnancies) are not
Winskill P, Walker P, Griffin J, et al., 2017, Modelling the cost-effectiveness of introducing the RTS,S malaria vaccine relative to scaling up other malaria interventions in sub-Saharan Africa, BMJ Global Health, Vol: 2, ISSN: 2059-7908
Objectives: To evaluate the relative cost-effectiveness of introducing the RTS,S malaria vaccine in sub-Saharan Africa compared with further scale-up of existing interventions.Design: A mathematical modelling and cost-effectiveness study.Setting: Sub-Saharan Africa.Participants: People of all ages.Interventions: The analysis considers the introduction and scale-up of the RTS,S malaria vaccine and the scale-up of long lasting insecticide treated bed nets (LLINs), indoor residual spraying (IRS) and seasonal malaria chemoprevention (SMC).Main outcome measure: The number of Plasmodium falciparum cases averted in all age groups over a ten year period.Results: Assuming access to treatment remains constant, increasing coverage of LLINs was consistently the most cost-effective intervention across a range of transmission settings and was found to occur early in the cost-effectiveness scale-up pathway. IRS, RTS,S and SMC entered the cost-effective pathway once LLIN coverage had been maximised. If non-linear production functions are included to capture the cost of reaching very high coverage, the resulting pathways become more complex and result in selection of multiple interventions.Conclusions: RTS,S was consistently implemented later in the cost-effectiveness pathway than the LLINs, IRS and SMC but was still of value as a fourth intervention in many settings to reduce burden to the levels set out in the international goals.
Routledge I, Chevez JER, Cucunuba Z, et al., 2017, UNDERSTANDING THE MALARIA TRANSMISSION PROCESS IN NEAR-ELIMINATION SETTINGS, 66th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 332-332, ISSN: 0002-9637
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