Abstract
BackgroundIntermittent preventive treatment in infants (IPTi) with sulphadoxine-pyrimethamine (SP) reduces the incidence of malaria episodes in young children. The exact mechanism by which the protective effect is mediated needs to be defined. This study aimed to investigate therapeutic, prophylactic, and possible exceeding effects of SP-based IPTi in two clinical trials.MethodsProtective efficacies from two IPTi trials performed in Kumasi, Ghana, and Lambaréné, Gabon, were assessed for overlapping time series of 61 days. For six-months periods after each of three IPTi doses a multivariate Poisson regression model with the respective cohort as co-variate was generated and effect modification of protective efficacy with time strata was evaluated by log-likelihood tests.ResultsProtective efficacies were not significantly different between the two study cohorts. Study-cohort corrected protective efficacy was highest for the first 61 days after each IPTi application and decreased continuously. For the first 61 days after IPTi-1, IPTi-2, and IPTi-3 the protective efficacy was 71%, 44%, and 43%, respectively. A reduction of the malaria incidence rate was detectable for the first 60, 30 and 40 days after IPTi-1, IPTi-2 and IPTi-3 drug application, respectively. After IPTi-3 a higher risk for malaria could be seen after day 60. This effect was mainly based on the overwhelming influence of the Kumasi cohort.ConclusionThe results suggest that SP-based IPTi mainly works through a therapeutic and prophylactic effect over 30 to 60 days after drug application and that a sustained effect beyond post-treatment prophylaxis might be very low.Trial registrationData analysis from clinical trials NCT ID # 00206739 (Kumasi Trial) and NCT ID # 00167843 (Lambaréné Trial), .
Highlights
Intermittent preventive treatment in infants (IPTi) with sulphadoxine-pyrimethamine (SP) reduces the incidence of malaria episodes in young children
Potential therapeutic effect of IPTi in dependence of application dose In the Kumasi cohort, prevalences of parasitaemia at time of IPTi-1, IPTi-2, and IPTi-3, were 14.8%, 18.2%, and 24.3%, respectively, expressing the proportion of IPTi applications with a potential therapeutic effect on sensitive strains
The efficacy of IPTi to protect from malaria episodes was between 17% and 62% in different African study areas resulting in an overall protective efficacy of about 25– 30% [6,9,10,11,12,13,14]
Summary
Intermittent preventive treatment in infants (IPTi) with sulphadoxine-pyrimethamine (SP) reduces the incidence of malaria episodes in young children. In most parts of sub-Saharan Africa individual control measures are restricted to the reduction of transmission by the use of insecticide-treated bed nets [2] and the treatment of malaria attacks [3], often with an ineffective drug due to parasite drug resistance [4]. Promising new approaches such as multi-stage vaccines [5] and intermittent preventive treatment in infants (IPTi) [6] aim to inhibit the multiplication of Plasmodium falciparum after infection. It has been suggested that the optimal drug application schedule depends on the half-life of the drug used, the extent of parasitic resistances against the drug, and the incidence of malaria in the area [8]
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