Evaluation of SPf66 malaria vaccine efficacy in Brazil.

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Abstract
This paper reports the efficacy results of the randomized, placebo-controlled, field trial of SPf66 malaria vaccine in Costa Marques, Rondonia, Brazil. This region is characterized by the seasonal distribution of Plasmodium falciparum and P. vivax infections, and the recent occupation by migrants from nonendemic areas. A total of 800 individuals of both sexes, ranging in age from seven to 60 years, were included in the study. Of the initial cohort, 572 participants completed the vaccination schedule. Clinical and parasitologic evaluations were obtained by active and passive searches on a periodic basis. The overall protective efficacy against P. falciparum infections was -1.6% (-32.9% to 22.4%), and 14.1% (-17.0% to 36.9%) for the first episode. The overall protective efficacy for P. vivax infections was -19.7% (-44.8% to 1.03%), and -10.8% (-41.1% to 12.8%) for the first episode. No statistical evidence of an overall significant protective effect of SPf66 malaria vaccine against P. falciparum and P. vivax malaria was obtained in this trial. The efficacy of the SPf66 malaria vaccine was evaluated in a randomized, placebo-controlled, field trial in Costa Marques, Rondonia, Brazil; a region characterized by seasonal Plasmodium falciparum and P. vivax infections and a recent influx of migrants from nonendemic areas. This vaccine is composed of sequences of 3 peptides from P. falciparum merozoite, erythrocytic stages, and a peptide from the circumsporozoite protein. Enrolled were 800 predominantly migrant men and women, 7-60 years of age, 572 of whom completed the vaccination schedule. Clinical and parasitologic evaluations were obtained by periodic active and passive searches up to Day 720. After the third dose, 5684 blood samples were collected and 967 (520 in the vaccine group and 447 in the placebo group) were positive. 212 P. falciparum infections (107 episodes in 76 participants in the vaccine group and 105 in 85 members of the placebo group) were confirmed after exclusion of relapses and treatment failures. A total of 427 P. vivax infections were detected (233 in 138 participants in the vaccine group and 194 in 127 participants in the placebo group). The overall protective efficacy against P. falciparum infections was -1.6% (95% confidence interval (CI), -32.9-22.4%) and 14.1% (95% CI, -17.0-36.9%) for the first episode. The overall protective efficacy for P. vivax infections was -19.7% (95% CI, -44.8-1.03%) and -10.8% (95% CI, -41.1-12.8%) for the first episode. These findings fail to provide evidence of an overall significant protective effect of the SPf66 malaria vaccine in this population.

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