Malaria Chemoprevention Efficacy Study Protocol – World



Preventive chemotherapy drugs are used, either alone or in combination, to prevent malaria infection and its consequences. This requires giving a full treatment course of antimalarial medication, often at predetermined intervals, to individuals who have not been diagnosed with malaria.
By providing anti-malarial medication to vulnerable populations, existing uncontrolled malaria infections are treated, and the drug provides a period of protection against new infections.
Chemoprevention strategies currently recommended by the World Health Organization (WHO) and covered by this guidance are described in Annex 1.
These include intermittent preventive treatment of malaria in pregnancy (IPTp), perennial malaria chemoprevention (PMC), seasonal malaria chemoprevention (SMC), and intermittent preventive treatment of malaria in school children (IPTsc) (1).

Information on the efficacy of the drugs used in these malaria chemoprevention strategies is important to ensure that the strategies remain effective in different settings with varying levels of drug resistance.
WHO has developed a standard protocol for therapeutic efficacy studies (TES), and tools for data analysis and monitoring of parasitemia and therapeutic responses to treatment (2). TES is a prospective evaluation of patients’ clinical and parasitic responses to treatment of complex malaria. TES is considered the gold standard for assessing anti-malarial drug treatment efficacy, and the resulting data are used to inform national malaria treatment policy in malaria endemic countries. Unfortunately, systematic reviews have demonstrated that even when TEs are performed at the same time and place, they do not accurately predict the efficacy of chemoprevention strategies (3). In TES, therapeutic efficacy in clearing asexual blood-stage parasites is evaluated in subjects with uncomplicated malaria. In chemoprevention, the given drug may work by clearing both asexual bloodstage parasites and pre-erythrocytic stage parasites in asymptomatic subjects. In both treatment and chemotherapy, many factors other than drug resistance affect efficacy, including immunity, drug absorption, and metabolism. A mutation that can significantly affect drug efficacy in clearing asexual blood-stage parasites may have a distinct effect on drug efficacy in clearing pre-erythrocytic stage parasites. Additionally, a low number of asexual blood-stage parasites in an asymptomatic recipient of chemoprevention may be easier to drug than a high number of asexual blood-stage parasites in a symptomatic patient enrolled in TES. Therefore specific protocols are needed to monitor chemoprevention efficacy.

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This document is intended as a guide to the study of chemoprevention efficacy and was developed based on reviews of protocols from ongoing studies. The document adopts some of the principles and practices underlying treatment efficacy monitoring to provide a standardized approach to monitoring and evaluating the efficacy of drugs used for malaria chemoprevention. This guide will be updated once additional experience is gained from chemoprevention efficacy studies.