Malaria vaccine

General information

For many years attempts have been made to find a vaccine against malaria, especially malaria tropica [ ]. Most of these attempts have been disappointing [ , ]. However, the results of a number of field studies have been reported.

SPf66 vaccine is a synthetic polypeptide based on pre-erythrocyte and asexual blood stage proteins of Plasmodium falciparum . A trial in Tanzania, in an area in which malaria is not only endemic, but the parasite load heavy, showed an estimated efficacy of 30% (95% CI = 0, 52%). The vaccine was immunogenic. There was also a difference in mortality between the groups, with one death among the vaccinated children and five in the control group. Adverse reactions were in general mild and similar to those in earlier work [ , ].

In Colombia, the vaccine brought about an immune response, and adverse effects were minimal. The first randomized, double-blind, controlled trial in Colombia, in which 1548 volunteers participated, showed an overall efficacy of 39%. In a small, selected group of volunteer soldiers there was a protective effect of 60–80%. In 96% of cases there were no adverse reactions and the adverse reactions in the remainder were mainly localized erythema, discomfort, and sometimes induration [ , ].

A study in Ecuador showed 67% mean prophylactic efficacy against P . falciparum , but the 95% CI were very wide (2.7, 89%). The vaccine was administered in three doses, at zero time and after 30 and 180 days. Adverse reactions (local pain, erythema, and local induration) occurred after the first dose in 6.2%, after the second dose in 19%, and after the third dose in 14%. The placebo group had similar adverse effects, but in a lower proportion of subjects and with fewer cases of induration. There was no protection against Plasmodium vivax infections [ ].

In a Venezuelan study [ ], 1442 villagers were vaccinated and vaccination was completed with the three doses in 976 subjects, with a comparison group of 938 subjects from the same area. Antibodies were produced against the vaccine. The adverse reactions were as in earlier work, but there was also some contralateral induration, mainly after the third dose of vaccine, which was given alternately into the left and right arms. Five women had generalized pruritus. Bronchospasm was observed in one case.

A recombinant vaccine has shown promise in vitro and in rabbits. It combines segments of 21 different immunogenic peptides from P . falciparum into a single recombinant protein, eliciting a multilayered immune response, including B cell and T cell responses [ ].