Evaluation of SPf66 malaria vaccine during a 22-month follow-up field trial in the Pacific coast of Colombia.

A double-blind randomized placebo-controlled field trial with the SPf66 malaria vaccine was carried out in an endemic area consisting of 14 small villages with exclusive fluvial access, in a rain forest area along the Rosario River, Colombia. A total of 1257 subjects completed the full three dose vaccination schedule on days 0, 30 and 180 (643 vaccinated group/623 placebo group) and were followed-up by passive and active surveillance over a period of 22 months. One hundred and thirty-four Plasmodium falciparum malaria episodes were detected (53 in vaccinated group/81 in placebo group), yielding an attack rate of 5.47 cases/100 person years of follow-up (pyears) in the vaccine group and 8.44/100 pyears in the placebo group. The estimated vaccine protective efficacy was 35.2% (95% CI 8.4-54.2%, P = 0.01). This result supports earlier findings that the SPf66 malaria vaccine diminishes the risk of infection by P. falciparum in endemic areas of South America.