IPTi, a strategy whereby infants are provided treatment doses of antimalarials at routine vaccination visits, has been shown to significantly reduce malaria and anemia in two studies in Tanzania. However the results obtained in Gabon are not similar. Many factors are likely to influence the efficacy or effectiveness IPTi. It is reasonable to assume that the efficacy of IPTi will be influenced markedly by the sensitivity of Plasmodium falciparum to the antimalarial drug (Sulfadoxine-Pyrimethamine) used for IPTi.

In order to interpret the results of individual IPTi trials conducted by the IPTi Consortium, and to provide information for policy makers regarding the predicted efficacy of IPTi, it is essential to obtain information on antimalarial drug sensitivity of Sulfadoxine-Pyrimethamine now that the IPTi trial has been conducted. The simplest and most universally accepted measure of testing for antimalarial drug efficacy is the "in vivo efficacy study," which follows a standardized World Health Organization protocol.

A second reason for evaluating drug resistance as an adjunct to the IPTi trials is to determine if the intervention increases the carriage and/or spread of drug resistant P. falciparum parasites.

Thirdly the overall effect at the community level of selection of resistant genotypes in IPTi-recipients is unclear.