RISK OF SEVERE MALARIA AMONG AFRICAN INFANTS - DIRECT EVIDENCE OF CLINICAL-PROTECTION DURING EARLY INFANCY

Little empirical evidence from field-based studies exists on the relat ive magnitude or duration of clinical protection from Plasmodium falci parum malaria in infancy. A prospective study was undertaken to examin e the age distribution of hospital admissions in four geographically a nd demographically well-defined areas with differing intensities of P. falciparum transmission. Where transmission was perennial, significan t clinical protection from severe morbidity was observed up to the thi rd month of life; in the seasonal transmission area, disease rates ros e after the sixth month of life. Infants exposed to the highest rates of P. falcipanrm exposure demonstrated significant declines in the ris ks of severe malaria from 6 months of age. These data provide direct e vidence for the very early acquisition of clinical immunity and for th e existence of a period of clinical protection, which together may exp lain why, in these communities, the cumulative risk of malarial diseas e throughout childhood appears to decline with increasing transmission intensity.