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Journal ArticleDOI

Plasmodium falciparum clearance in clinical studies of artesunate-amodiaquine and comparator treatments in sub-Saharan Africa, 1999–2009

TL;DR: Within the period covered by these studies, rapid Plasmodium falciparum clearance continues to be achieved in Sub-Saharan African patients treated with ACT, and in particular with ASAQ, and the prediction formula for parasite clearance time could be a pragmatic tool for studies with binary outcomes and once-daily sampling.
Abstract: Artemisinin-based combination therapy (ACT) is the recommended first-line therapy for uncomplicated Plasmodium falciparum malaria worldwide but decreased artemisinin susceptibility, phenotypically characterized as slow parasite clearance time (PCT), has now been reported in Southeast Asia. This makes it all too important to measure the dynamics of parasite clearance in African patients treated with ACT over time, to understand trends and detect changes early enough to intervene Individual patient data from 27 clinical trials of artesunate-amodiaquine (ASAQ) vs comparators conducted between 1999 and 2009 were analysed for parasite clearance on modified intent-to-treat (ITT) basis. Overall 15,017 patients treated for uncomplicated P. falciparum malaria at 44 sites in 20 sub-Saharan African countries were included in the analysis; 51% (n=7,660) vs 49% (n=7,357) were treated with ASAQ and comparator treatments, respectively. Seventy-seven per cent (77%) were children under six years of age. The proportion of the patients treated with ASAQ with persistent parasitaemia on Day 2 was 8.6%, and 1.5% on Day 3. Risk factor for not clearing parasites on Day 2 and Day 3 calculated by multivariate logistic regression with random effect on site and controlling for treatment were: high parasitaemia before treatment was (adjusted risk ratios (AOR) 2.12, 95% CI 1.91-2.35, AOR 2.43, 95% CI 1.98-3.00, respectively); non-ACT treatment (p=0.001, for all comparisons). Anaemia (p=0.001) was an additional factor for Day 2 and young age (p=0.005) for Day 3. In patients treated with ASAQ in studies who had complete parasitaemia data every 24 hours up to Day 3 and additionally Day 7, the parasite reduction ratio was 93.9% by Day 1 and 99.9% by Day 2. Using the median parasitaemia before treatment (p0=27,125 μL) and a fitted model, the predicted PCT (pPCT = 3.614*ln (p0) – 6.135, r² = 0.94) in ASAQ recipients was 31 hours. Within the period covered by these studies, rapid Plasmodium falciparum clearance continues to be achieved in Sub-Saharan African patients treated with ACT, and in particular with ASAQ. The prediction formula for parasite clearance time could be a pragmatic tool for studies with binary outcomes and once-daily sampling, both for research and monitoring purposes.

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Journal ArticleDOI
21 Aug 2014-PLOS ONE
TL;DR: The prevalence of K13-propeller and FP2 polymorphisms did not increase over time, and was not associated with either time since prior receipt of an ACT or the persistence of parasites ≥2 days following treatment with an ACT, indicating that artemisinin resistance is not prevalent in Uganda.
Abstract: The emergence of resistance to artemisinin derivatives in Southeast Asia, manifested as delayed clearance of Plasmodium falciparum following treatment with artemisinins, is a major concern. Recently, the artemisinin resistance phenotype was attributed to mutations in portions of a P. falciparum gene (PF3D7_1343700) encoding kelch (K13) propeller domains, providing a molecular marker to monitor the spread of resistance. The P. falciparum cysteine protease falcipain-2 (FP2; PF3D7_1115700) has been shown to contribute to artemisinin action, as hemoglobin degradation is required for potent drug activity, and a stop mutation in the FP2 gene was identified in parasites selected for artemisinin resistance. Although delayed parasite clearance after artemisinin-based combination therapy (ACT) has not yet been noted in Uganda and ACTs remain highly efficacious, characterizing the diversity of these genes is important to assess the potential for resistance selection and to provide a baseline for future surveillance. We therefore sequenced the K13-propeller domain and FP2 gene in P. falciparum isolates from children previously treated with ACT in Uganda, including samples from 2006–7 (n = 49) and from 2010–12 (n = 175). Using 3D7 as the reference genome, we identified 5 non-synonymous polymorphisms in the K13-propeller domain (133 isolates) and 35 in FP2 (160 isolates); these did not include the polymorphisms recently associated with resistance after in vitro selection or identified in isolates from Asia. The prevalence of K13-propeller and FP2 polymorphisms did not increase over time, and was not associated with either time since prior receipt of an ACT or the persistence of parasites ≥2 days following treatment with an ACT. Thus, the K13-propeller and FP2 polymorphisms associated with artemisinin resistance are not prevalent in Uganda, and we did not see evidence for selection of polymorphisms in these genes.

115 citations


Cites background from "Plasmodium falciparum clearance in ..."

  • ...Second, as delayed clearance of parasites after therapy is uncommon and associated with high baseline parasitemia in Uganda, persistent parasitemia 2 days after the onset of therapy is likely not a reliable indicator of resistance [6,8]....

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Journal ArticleDOI
TL;DR: There is a significant change in parasite genotype, with key molecular determinants of AL selection almost reaching saturation, and there is need to closely monitor parasite genotypic, phenotypic and clinical dynamics in response to continued use of AL in western Kenya.
Abstract: Artemether–lumefantrine (AL) became the first-line treatment for uncomplicated malaria in Kenya in 2006. Studies have shown AL selects for SNPs in pfcrt and pfmdr1 genes in recurring parasites compared to the baseline infections. The genotypes associated with AL selection are K76 in pfcrt and N86, 184F and D1246 in pfmdr1. To assess the temporal change of these genotypes in western Kenya, 47 parasite isolates collected before (pre-ACT; 1995–2003) and 745 after (post-ACT; 2008–2014) introduction of AL were analyzed. In addition, the associations of parasite haplotype against the IC50 of artemether and lumefantrine, and clearance rates were determined. Parasite genomic DNA collected between 1995 and 2014 was analyzed by sequencing or PCR-based single-base extension on Sequenom MassARRAY. IC50s were determined for a subset of the samples. One hundred eighteen samples from 2013 to 2014 were from an efficacy trial of which 68 had clearance half-lives. Data revealed there were significant differences between pre-ACT and post-ACT genotypes at the four codons (chi-square analysis; p < 0.0001). The prevalence of pfcrt K76 and N86 increased from 6.4% in 1995–1996 to 93.2% in 2014 and 0.0% in 2002–2003 to 92.4% in 2014 respectively. Analysis of parasites carrying pure alleles of K + NFD or T + YYY haplotypes revealed that 100.0% of the pre-ACT parasites carried T + YYY and 99.3% of post-ACT parasites carried K + NFD. There was significant correlation (p = 0.04) between lumefantrine IC50 and polymorphism at pfmdr1 codon 184. There was no difference in parasite clearance half-lives based on genetic haplotype profiles. This study shows there is a significant change in parasite genotype, with key molecular determinants of AL selection almost reaching saturation. The implications of these findings are not clear since AL remains highly efficacious. However, there is need to closely monitor parasite genotypic, phenotypic and clinical dynamics in response to continued use of AL in western Kenya.

36 citations


Cites background from "Plasmodium falciparum clearance in ..."

  • ...However, ACTs remain highly efficacious in subSaharan Africa (SSA) with fast clearance half-lives (Ashley et al., 2014; Zwang et al., 2014)....

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Journal ArticleDOI
TL;DR: This study demonstrated the absence of k13-resistant genotypes in P. falciparum isolates from Cameroon, giving a baseline for the long-term monitoring of artemisinin derivative efficacy in Africa.
Abstract: The spread of Plasmodium falciparum resistance to artemisinin derivatives in Southeast Asia is a major source of concern and the emergence of resistance in Africa would have dramatic consequences, by increasing malaria mortality and morbidity. It is therefore urgent to implement regular monitoring in sentinel sites in sub-Saharan Africa using robust and easy-to-implement tools. The prevalence of k13-propeller mutations and the phenotypic profiles are poorly known in sub-Saharan Africa. Here, the k13-propeller polymorphism was compared to both ex vivo susceptibility to DHA and early parasitological and clinical responses to artemisinin combination therapy (ACT). Plasmodium falciparum isolates were collected in 2015 in Yaounde (Cameroon) from patients treated with dihydroartemisinin-piperaquine combination. Samples were analysed for their susceptibility to artemisinin using the k13-propeller sequencing, the ex vivo ring-stage survival assay, the in vivo parasite positive rate and the clinical statute at day 2. None of the collected isolates revealed the presence of resistance mutations in the k13-propeller sequence. The median ring-stage survival rate for all the 64 interpretable isolates after a 6-hour pulse of 700 nM dihydroartemisinin was low, 0.49% (IQR: 0–1.3). Total parasite clearance was observed for 87.5% of patients and the remaining parasitaemic isolates (12.5%) showed a high reduction of parasite load, ranging from 97.5 to 99.9%. Clinical symptoms disappeared in 92.8% of cases. This study demonstrated the absence of k13-resistant genotypes in P. falciparum isolates from Cameroon. Only synonymous mutations were found with a low prevalence (4.3%). A good association between k13 genotypes and the ex vivo ring-stage survival assay or parasitological and clinical data was obtained. These results give a baseline for the long-term monitoring of artemisinin derivative efficacy in Africa.

23 citations

Journal ArticleDOI
TL;DR: The results demonstrate the potent preclinical antileukemic activity of ARTS as well as its potential for a rapid transition to a clinical trial either alone or in combination with conventional chemotherapy or BCL-2 inhibitor, for treatment of AML.

22 citations

Journal ArticleDOI
TL;DR: An analysis of P. falciparum genetic diversity, focusing on antimalarial resistance-associated molecular markers in two socioeconomically different villages in mainland Equatorial Guinea, suggests that closer monitoring should be maintained to prevent the possible spread of artemisinin resistance in Africa.
Abstract: Efforts to control malaria may affect malaria parasite genetic variability and drug resistance, the latter of which is associated with genetic events that promote mechanisms to escape drug action. The worldwide spread of drug resistance has been a major obstacle to controlling Plasmodium falciparum malaria, and thus the study of the origin and spread of associated mutations may provide some insights into the prevention of its emergence. This study reports an analysis of P. falciparum genetic diversity, focusing on antimalarial resistance-associated molecular markers in two socioeconomically different villages in mainland Equatorial Guinea. The present study took place 8 years after a previous one, allowing the analysis of results before and after the introduction of an artemisinin-based combination therapy (ACT), i.e., artesunate plus amodiaquine. Genetic diversity was assessed by analysis of the Pfmsp2 gene and neutral microsatellite loci. Pfdhps and Pfdhfr alleles associated with sulfadoxine-pyrimethamine (SP) resistance and flanking microsatellite loci were investigated, and the prevalences of drug resistance-associated point mutations of the Pfcrt, Pfmdr1, Pfdhfr, and Pfdhps genes were estimated. Further, to monitor the use of ACT, we provide the baseline prevalences of K13 propeller mutations and Pfmdr1 copy numbers. After 8 years, noticeable differences occurred in the distribution of genotypes conferring resistance to chloroquine and SP, and the spread of mutated genotypes differed according to the setting. Regarding artemisinin resistance, although mutations reported as being linked to artemisinin resistance were not present at the time, several single nucleotide polymorphisms (SNPs) were observed in the K13 gene, suggesting that closer monitoring should be maintained to prevent the possible spread of artemisinin resistance in Africa.

17 citations


Cites background from "Plasmodium falciparum clearance in ..."

  • ...falciparum resistance to artemisinin derivatives in Southeast Asia (where it was introduced for the first time in the mid-1990s), but so far it has not been detected in Africa (13)....

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References
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Journal ArticleDOI
TL;DR: Both AS/AQ and AS/SP are highly efficacious in Dabola, whereas there is molecular evidence of established SP resistance in Laine, which supports the choice of the national programme of Guinea to adopt AS/ aQ as first line antimalarial treatment.
Abstract: In the last five years, countries have been faced with changing their malaria treatment policy to an artemisinin-based combination therapy (ACT), many with no national data on which to base their decision. This is particularly true for a number of West African countries, including Guinea, where these studies were performed. Two studies were conducted in 2004/2005 in programmes supported by Medecins Sans Frontieres, when chloroquine was still national policy, but artesunate (AS)/sulphadoxine-pyrimethamine (SP) had been used in refugee camps for two years. In Dabola (central Guinea), 220 children aged 6–59 months with falciparum malaria were randomized to receive either AS/amodiaquine (AQ) or AS/SP. In vivo efficacy was assessed following the 2003 World Health Organization guidelines. In a refugee camp in Laine (south of Guinea), where an in vivo study was not feasible due to the unstable context, a molecular genotyping study in 160 patients assessed the prevalence of mutations in the dihydrofolate reductase (dhfr) (codons 108, 51, 59) and dihydropteroate synthase (dhps) (codons 436, 437, 540) genes of Plasmodium falciparum, which have been associated with resistance to pyrimethamine and sulphadoxine, respectively. In Dabola, after 28 days of follow-up, Polymerase Chain Reaction (PCR)-adjusted failure rates were 1.0% (95%CI 0–5.3) for AS/AQ and 1.0% (95%CI 0–5.5) for AS/SP. In the refugee camp in Laine, the molecular genotyping study found three dhfr mutations in 85.6% (95%CI 79.2–90.7) patients and quintuple dhfr/dhps mutations in 9.6% (95%CI 5.2–15.9). Both AS/AQ and AS/SP are highly efficacious in Dabola, whereas there is molecular evidence of established SP resistance in Laine. This supports the choice of the national programme of Guinea to adopt AS/AQ as first line antimalarial treatment. The results highlight the difficulties faced by control programmes, which have gone through the upheaval of implementing ACTs, but cannot predict how long their therapeutic life will be, especially in countries which have chosen drugs also available as monotherapies.

39 citations


"Plasmodium falciparum clearance in ..." refers background or methods in this paper

  • ...We would like to thank Epicentre, Paris, France, for sharing the datasets [23,29-32,34-36] and all the principal investigators of the other studies....

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  • ...Details of the studies can be found elsewhere [26-40]....

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Journal ArticleDOI
TL;DR: A preliminary economic assessment of the proposed artemisinin‐based combinations for treating falciparum malaria in Senegal finds that implementing AS‐AQ for slide‐proven malaria would be US$8150 (53% less expensive) and studies examining the public health effect and economics of deploying AS‐ aQ on a wider scale are underway in Senegal.
Abstract: Senegal is changing policy for case management of uncomplicated falciparum malaria, which hitherto is diagnosed clinically and treated with chloroquine or intramuscular quinine. The WHO recommends artemisinin-based combinations for treating falciparum malaria, preferably based on a parasitological diagnosis. There are no economic projections if such a policy were introduced in Senegal. We have conducted a preliminary economic assessment of such a policy change. The study took place in the chloroquine-resistant district of Oussouye in south-western Senegal. We reviewed clinic registers of the district health posts (n ¼ 5) from 1996 to 2001, and piloted artesunate combined with amodiaquine (at 4 and 10 mg/kg/day · 3 days respectively) (AS-AQ) for treating slide-proven falciparum malaria during two rainy seasons (2000 and 2001) at one health centre. These data were used to calculate current direct patient costs (clinic visit, diagnosis, drugs) of malaria treatment and project future costs for the district. The robustness of the model was tested by allowing for different drug failure rates and costs of diagnosis. During 1996-2001, the mean number of primary treatments per year was 7654 for a mean, direct cost of US$17 452 to the community. Clinical diagnosis resulted in over-treatment : 56% and 66% in the wet and dry seasons respectively. Current policy leads to substantial drug wastage and excess direct costs for the community. The direct costs of implementing AS-AQ for slide-proven malaria would be US$8150 (53% less expensive). Studies examining the public health effect and economics of deploying AS-AQ on a wider scale are underway in Senegal.

36 citations


"Plasmodium falciparum clearance in ..." refers background in this paper

  • ...Table 4 Clearance reduction, artesunate/amodiaquine groups Country site Parasitaemia, geometric mean N Parasite reduction ratio (individual data) d1/d0 d2/d0 d3/d0 d7/d0 Burkina faso - Nanoro 2008 21,185 295 97.8% 100.0% 100.0% 100.0% Cameroon 2006 24,129 110 97.0% 100.0% 100.0% 100.0% Gabon - Fougamou 2008 21,117 80 98.6% 100.0% 100.0% 100.0% Gabon 1999 20,867 108 98.2% 100.0% 100.0% 100.0% Kenya 1999 30,040 199 94.5% 99.9% 100.0% 100.0% Kenya 2009 12,193 54 99.2% 100.0% 100.0% 100.0% Madagascar 2006 9,648 119 98.9% 100.0% 100.0% 100.0% Mali Bougoula 2006 23,744 135 93.8% 99.9% 100.0% 100.0% Mozambique - Manhica 2008 35,924 210 77.1% 99.8% 100.0% 100.0% Nigeria - Afokang 2008 20,326 92 96.3% 99.7% 100.0% 100.0% Nigeria - Pamol 2008 17,329 82 97.9% 99.8% 100.0% 100.0% Senegal 1999 41,753 160 89.5% 99.8% 100.0% 100.0% Senegal 2006 20,201 264 91.4% 99.7% 100.0% 100.0% Uganda - Mbarara 2008 27,262 160 98.4% 100.0% 100.0% 100.0% Zambia - Ndola 2008 35,887 85 91.9% 100.0% 100.0% 100.0% Zanzibar Kivunge 2002 20,625 148 95.7% 100.0% 100.0% 100.0% Zanzibar Micheweni 2002 18,236 54 95.2% 99.7% 100.0% 100.0% Total 23,596 2355 93.9% 99.9% 100.0% 100.0%...

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  • ...5Department of Parasitology, Faculty of Medicine, Cheikh Anta Diop University, Dakar, Sénégal....

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  • ...8Institut de Recherche pour le Développement (IRD) Unité mixte de Recherche 198, Dakar BP 1386, Sénégal....

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  • ...Out of the 27 studies included (conducted between 1999 and 2009), three were multi-country studies [17-19], two studies compared ASAQ fixed and loose combination [20-22] and three studies were non-comparative (in Sierra Leone [23] and Senegal [24,25])....

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Journal ArticleDOI
TL;DR: These results highlight the normal distribution of early parasitological responses following ACT, and the influence that heterogeneity in study design, host and parasite factors have in confounding a surveillance system based on Day 3 parasite positivity.
Abstract: Background: Parasitaemia on Day 3 has been proposed as a useful alert of potential artemisinin resistance, however, the normal variation of parasite clearance observed in artemisinin-based combination therapy clinical trials is poorly documented. Methods: The trends in early parasitological response following treatment with an artemisinin anti-malarial regimen were reviewed. A PubMed literature search identified all studies using an artemisinin regimen for uncomplicated falciparum malaria published between January 2000 and December 2011. Data from clinical studies were extracted for analysis using a standardized questionnaire. Results: In total 65,078 patients were enrolled into 213 clinical trials with 413 treatment arms containing either an artemisinin derivative alone (n=26) or in combination with a partner drug (n=387). The proportion of patients remaining parasitaemic at 24, 48 and 72 hours was documented in 115 (28%), 167 (40%) and 153 (37%) treatment arms, respectively. Excluding resistance studies in Cambodia, the median proportion of patients still parasitaemic was 53.8% [range 3–95, IQR=30.5-69.2] on Day 1, 6% [range 0–65.9, IQR=2-11.5] on Day 2 and 0 [range 0–12.6, IQR=0-2] on Day 3. Comparing studies from 2000 to 2005 and 2006 to 2011, the median proportion of patients reported to remain parasitaemic at 72 hours decreased in Africa (1.2% vs 0%, p=0.007), but increased in Asia (0.4% vs 3.9%, p=0.076). In 95% of studies the proportion of patients with peripheral parasitaemia was less than 6% at 72 hours. Conclusions: These results highlight the normal distribution of early parasitological responses following ACT, and the influence that heterogeneity in study design, host and parasite factors have in confounding a surveillance system based on Day 3 parasite positivity. Greater understanding of factors influencing parasite clearance is crucial, but will require analysis of pooled data from individual patient records.

36 citations


"Plasmodium falciparum clearance in ..." refers background in this paper

  • ...However, as of today, in the clinic as well as in the field the parasite clearance time (PCT) and its related clinical phenotype (delayed PCT) remain the best practical surrogates of artemisinin in vivo resistance [8]; the problem is that the frequent sampling (every six or eight hours) required to measure PCT accurately and to estimate the parasite clearance half-life [9] is practically difficult even in research settings....

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Journal ArticleDOI
TL;DR: Both ASAQ and AL were highly efficacious and ASAQ was non-inferior to AL and the proportion of patients with re-infection was high in both arms in this highly endemic setting.
Abstract: Prospective efficacy monitoring of anti-malarial treatments is imperative for timely detection of resistance development. The in vivo efficacy of artesunate-amodiaquine (ASAQ) fixed-dose combination (FDC) was compared to that of artemether-lumefantrine (AL) among children aged six to 59 months in Nimba County, Liberia, where Plasmodium falciparum malaria is endemic and efficacy data are scarce. An open-label, randomized controlled non-inferiority trial compared the genotyping adjusted day 42 cure rates of ASAQ FDC (ASAQ Winthrop®) to AL (Coartem®) in 300 children aged six to 59 months with uncomplicated falciparum malaria. Inclusion was between December 2008 and May 2009. Randomization (1:1) was to a three-day observed oral regimen (ASAQ: once a day; AL: twice a day, given with fatty food). Day 7 desethylamodiaquine and lumefantrine blood-concentrations were also measured. The day 42 genotyping-adjusted cure rate estimates were 97.3% [95% CI: 91.6-99.1] for ASAQ and 94.2% [88.1-97.2] for AL (Kaplan-Meier survival estimates). The difference in day 42 cure rates was −3.1% [upper limit 95% CI: 1.2%]. These results were confirmed by observed proportion of patients cured at day 42 on the per-protocol population. Parasite clearance was 100% (ASAQ) and 99.3% (AL) on day 3. The probability to remain free of re-infection was 0.55 [95% CI: 0.46-0.63] (ASAQ) and 0.66 [0.57-0.73] (AL) (p = 0.017). Both ASAQ and AL were highly efficacious and ASAQ was non-inferior to AL. The proportion of patients with re-infection was high in both arms in this highly endemic setting. In 2010, ASAQ FDC was adopted as the first-line national treatment in Liberia. Continuous efficacy monitoring is recommended. The protocols were registered with Current Controlled Trials, under the identifier numbers ISRCTN51688713 , ISRCTN40020296 .

32 citations

Journal ArticleDOI
TL;DR: In 2004, Sierra Leone adopted artesunate plus amodiaquine as first‐line antimalarial treatment and evaluated the efficacy of this combination in Kailahun, where a previous study had shown 70.2% efficacy of amodIAquine in monotherapy.
Abstract: OBJECTIVE: In 2004, Sierra Leone adopted artesunate plus amodiaquine as first-line antimalarial treatment. We evaluated the efficacy of this combination in Kailahun, where a previous study had shown 70.2% efficacy of amodiaquine in monotherapy. METHODS: Method and outcome classification of the study complied with WHO guidelines. Children 6-59 months with uncomplicated malaria were followed-up for 28 days. PCR genotyping was used to distinguish recrudescence from reinfection. Reinfections were reclassified as cured. RESULTS: Of 172 children who were referred to the study clinic, 126 satisfied inclusion criteria and were enrolled. No early treatment failures were reported. The day 14, efficacy was 98.2% (95% CI: 93.8-99.8). Of 65 recurrent parasitaemias analysed by PCR, 17 were recrudescences. The PCR-adjusted day 28 efficacy was 84.5% (95% CI: 76.4-90.7). All true failures occurred in the last 8 days of follow-up. Of 110 children who completed the 28-day follow-up, 54 (49.1%) experienced a novel infection. CONCLUSION: The efficacy of this combination was disappointing. The high reinfection rate suggested little prophylactic effect. In Kailahun a more efficacious combination might be necessary in the future. The efficacy of AS + AQ needs to be monitored in Kailahun and in the other regions of Sierra Leone.

20 citations


"Plasmodium falciparum clearance in ..." refers background or methods in this paper

  • ...Out of the 27 studies included (conducted between 1999 and 2009), three were multi-country studies [17-19], two studies compared ASAQ fixed and loose combination [20-22] and three studies were non-comparative (in Sierra Leone [23] and Senegal [24,25])....

    [...]

  • ...We would like to thank Epicentre, Paris, France, for sharing the datasets [23,29-32,34-36] and all the principal investigators of the other studies....

    [...]

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