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Efficacy trial of malaria vaccine SPf66 in Gambian infants
U D'Alessandro1, A Leach, C J Drakeley
1Medical Research Council Laboratories, Banjul, The Gambia.
Insights
The SPf66 malaria vaccine showed minimal protection against clinical malaria in Gambian infants, with only 8% efficacy against the first episode. This study did not find significant differences in malaria incidence between vaccinated and placebo groups.
Area of Science:
- Immunology
- Tropical Medicine
- Vaccinology
Background:
- The SPf66 vaccine is a synthetic protein vaccine targeting Plasmodium falciparum malaria.
- Previous studies in Tanzania and South America indicated some protective efficacy for SPf66.
Purpose of the Study:
- To evaluate the efficacy of the SPf66 malaria vaccine in Gambian infants.
- To assess protection against clinical Plasmodium falciparum malaria in a high-transmission area.
Main Methods:
- A randomized, double-blind, placebo-controlled trial involving 630 infants aged 6-11 months.
- Participants received three doses of SPf66 or injected polio vaccine (IPV).
- Morbidity was monitored via active and passive case detection during the rainy season.
Main Results:
- SPf66 vaccine showed 8% protective efficacy against the first clinical malaria episode (95% CI -18 to 29).
- Overall incidence of clinical malaria episodes had 3% protective efficacy (95% CI -24 to 24).
- No significant differences in mortality, health center admissions, or parasite rates were observed.
Conclusions:
- The SPf66 vaccine did not achieve significant protection against clinical malaria in Gambian infants.
- Study findings contrast with previous SPf66 efficacy reports from other regions.
- Further research may be needed to understand vaccine performance in different transmission settings.
Abstract:
SPf66 malaria vaccine is a synthetic protein with aminoacid sequences derived from pre-erythrocytic and asexual blood-stage proteins of Plasmodium falciparum. SPf66 was found to have a 31% protective efficacy in an area of intensive malaria transmission in Tanzanian children, 1-5 years old. We report a randomised, double-blind, placebo-controlled trial of SPf66 against clinical P falciparum malaria in Gambian infants. 630 children, aged 6-11 months at time of the first dose, received three doses of SPf66 or injected polio vaccine (IPV). Morbidity was monitored during the following rainy season by means of active and passive case detection. Cross-sectional surveys were carried out at the beginning and at the end of the rainy season. An episode of clinical malaria was defined as fever (> or = 37.5 degrees C) and a parasite density of 6000/microL or more. Analysis of efficacy was done on 547 children (316 SPf66/231 IPV). No differences in mortality or in health centre admissions were found between the two groups of children. 347 clinical episodes of malaria were detected during the three and a half months of surveillance. SPf66 vaccine was associated with a protective efficacy against the first or only clinical episode of 8% (95% CI -18 to 29, p = 0.50) and against the overall incidence of clinical episodes of malaria of 3% (95% CI -24 to 24, p = 0.81). No significant differences in parasite rates or in any other index of malaria were found between the two groups of children. The findings of this study differ from previous reports on SPf66 efficacy from South America and from Tanzania. In The Gambia, protection against clinical attacks of malaria during the rainy season after immunisation in children 6-11 months old at time of the first dose was not achieved.