A POPULATION-BASED CLINICAL-TRIAL WITH THE SPF66 SYNTHETIC PLASMODIUM-FALCIPARUM MALARIA VACCINE IN VENEZUELA

A phase III malaria vaccine trial in 13 villages in an endemic area, S outh Venezuela, compared incidence rates of Plasmodium falciparum and Plasmodium vivax infections in 1422 vaccinated and 938 nonvaccinated s ubjects over 18 months. The SPf66 vaccine was given in three doses, on days 0, 20, and 112. Vaccination was complete in 976 subjects (68.7%) . Minor side effects requiring no treatment were reported by 123 (12.6 %), with an apparent increase in frequency from the first to the third vaccine dose. No autoimmune evidence was observed in a sample of subj ects. Antibodies against SPf66 were present at low titers in 24.7% of tested subjects before vaccination, increasing to 53.6% after the seco nd dose and to 73.6% after the third dose; 26.4% of subjects initially seronegative never seroconverted. The SPf66 malaria vaccine showed a protective efficacy of 55% (95% confidence interval, 21%-75%) against P. falciparum and of 41% (19%-57%) against P. vivax malaria.