The immunogenicity of anti-malaria synthetic vaccine SPf66 was tested in a
region of the Colombian middle Atrato river. The specific serum antibodies
against SPf66 were quantified in vaccinees and placebo injected controls
for a two-years period post-immunization. The frequency of individuals
showing seroconversion of anti-SPf66 antibodies three months after
completion of the immunization schedule was higher in vaccinees than in
controls (52.7% and 25.5%, respectively, p{0.01). However, an over than
four-fold increase of the specific anti-SPf66 antibody titers was observed
only in 1.4% of vaccinees and 0.2% of the controls (p{0.01). The anti-SPf66
antibody titers augmented in vaccinees from first dose application to three
months after the third dose, continuously decreasing thereafter to reach
below baseline values two years after completion of the immunization
schedule. The results show that SPf66 has very low immunogenicity and
induces a short term humoral immune response (six months). {P}