Observations on the early course of untreated falciparum malaria in semi-immune African children following a short period of protection.

The early course of new malarial infections was observed, in a highly malarious area of East Africa, in a group of schoolchildren who had been protected from infection for between one and two months by the administration of antimalarial drugs. Many of the new infections caused clinical symptoms of malaria and a parasitaemia that was significantly greater than had prevailed generally before treatment. It was concluded that even the short period of a few weeks of drug protection against malarial infection had lowered the immunity of the children to an appreciable degree. This observation tends to support other evidence of the lability of the anti-parasite defence mechanism.