SPf66 Malaria Vaccine: Tanzanian Trial Results

The results of what is considered the toughest trial to date of the controversial Colombian malaria vaccine, SPf66, carried out in Tanzania, are equivocal and do not provide clear evidence of protective efficacy. The data are published in The Lancet (October 29).

After encouraging results from studies in South America which indicated a protective efficacy against Plasmodium falciparum ranging from 39%-67% (albeit with wide confidence intervals), the results of the Tanzanian trial were awaited with some anticipation. In South America malarial transmission is low, while in Tanzania transmission is intense.

A total of 586 children aged one to five years received three doses of SPf66 or placebo, and the incidence and density of parasitemia were assessed through repeated cross-sectional surveys on subgroups of the children. Morbidity was assessed over a one-year period by passive case detection in all children and active case detection in a subgroup of 191. Clinical malaria was defined as fever and blood parasite density of greater than 20,000 units per microliter.