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A pilot safety and immunogenicity study of the malaria vaccine SPf66 in Gambian infants
A Leach1, C J Drakeley, U D'Alessandro
1MRC Laboratories, Fajara, Banjul, The Gambia.
Insights
The SPf66 malaria vaccine showed modest local reactions in Gambian infants. While immunogenic, antibody levels waned, and malaria incidence was higher in vaccinated children compared to controls.
Area of Science:
- * Tropical Medicine
- * Vaccinology
- * Pediatric Infectious Diseases
Background:
- * The SPf66 vaccine represents a significant effort in malaria prevention research.
- * Pilot trials are crucial for assessing the safety and immunogenicity of new vaccine candidates in target populations.
Purpose of the Study:
- * To evaluate the safety and immunogenicity of the SPf66 malaria vaccine in Gambian infants.
- * To compare the immunogenicity of SPf66 produced in Colombia versus the USA.
- * To assess the impact of different SPf66 dosage levels on antibody response.
Main Methods:
- * A pilot trial involving 150 Gambian infants.
- * Administration of SPf66 vaccine at 0.5 mg and 1.0 mg doses.
- * Monitoring for systemic and local adverse reactions.
- * Measurement of antibody levels post-vaccination.
- * Comparison with a control group receiving inactivated polio vaccine.
Main Results:
- * No significant systemic side effects were observed; mild local reactions occurred after the third 1.0 mg dose.
- * Colombian-produced SPf66 was more immunogenic than US-produced SPf66.
- * A 1.0 mg dose elicited higher antibody levels than a 0.5 mg dose.
- * Antibody levels declined rapidly after the third dose and remained low during the malaria season.
- * Higher incidence of clinical malaria was observed in SPf66 recipients versus polio vaccine recipients.
Conclusions:
- * SPf66 demonstrated an acceptable safety profile in Gambian infants, with manageable local reactions.
- * Immunogenicity varied by vaccine origin and dose, but antibody levels were not sustained.
- * The observed increase in malaria incidence warrants further investigation, although the trial was not powered to assess efficacy.
Abstract:
A pilot safety and immunogenicity trial of the malaria vaccine SPf66 has been undertaken in 150 Gambian infants. No significant systemic side effects were recorded but modest local reactions were seen after the administration of a third 1.0 mg dose. SPf66 produced in Colombia was more immunogenic than SPf66 produced in the USA and a 1.0 mg dose of each vaccine gave higher antibody levels than a 0.5 mg dose. However, antibody levels fell rapidly after administration of the third dose of vaccine and showed little change over the following malaria transmission season. The incidence of clinical malaria was higher among children who received SPf66 than among children who received inactivated polio vaccine, the effect being most marked among children who received 1.0 mg Colombian SPf66. As the trial was not designed to measure the effect of SPf66 on morbidity from malaria, the significance of this finding is uncertain.