Malaria chemoprophylaxis with chloroquine in young Nigerian children. I. Its effect on mortality, morbidity and the prevalence of malaria.

One hundred and ninety-eight Nigerian children who received weekly chemoprophylaxis with chloroquine from shortly after birth until the age of one year or two years and 185 age-matched controls were studied. Chemoprophylaxis with chloroquine was partially, but not completely, effective in controlling malaria. Clinical malaria was documented significantly less frequently in protected children than in control children, and only 9% of random blood films obtained from protected children were positive for Plasmodium falciparum while 41% of random blood films from control children were positive for this parasite. Mean malaria antibody levels were lower in protected than in control children; for ELISA and precipitin antibodies the difference between the two groups was less marked at two years than at one year. Mortality was similar among protected and among control children. No rebound mortality or morbidity was observed after chemoprophylaxis was stopped.