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Lancet. 2001 Dec 8;358(9297):1927-34.

Efficacy of RTS,S/AS02 malaria vaccine against Plasmodium falciparum infection in semi-immune adult men in The Gambia: a randomised trial.

Author information

1
Medical Research Council Laboratories, PO Box 273, The, Banjul, Gambia. kbojang@mrc.gm

Abstract

BACKGROUND:

RTS,S/AS02 is a pre-erythrocytic malaria vaccine based on the circumsporozoite surface protein of Plasmodium falciparum fused to HBsAg, incorporating a new adjuvant (AS02). We did a randomised trial of the efficacy of RTS,S/AS02 against natural P. falciparum infection in semi-immune adult men in The Gambia.

METHODS:

306 men aged 18-45 years were randomly assigned three doses of either RTS,S/AS02 or rabies vaccine (control). Volunteers were given sulfadoxine/pyrimethamine 2 weeks before dose 3, and kept under surveillance throughout the malaria transmission season. Blood smears were collected once a week and whenever a volunteer developed symptoms compatible with malaria. The primary endpoint was time to first infection with P. falciparum. Analysis was per protocol.

FINDINGS:

250 men (131 in the RTS,S/AS02 group and 119 in the control group) received three doses of vaccine and were followed up for 15 weeks. RTS,S/AS02 was safe and well tolerated. P. falciparum infections occurred significantly earlier in the control group than the RTS,S/AS02 group (Wilcoxon's test p=0.018). Vaccine efficacy, adjusted for confounders, was 34% (95% CI 8.0-53, p=0.014). Protection seemed to wane: estimated efficacy during the first 9 weeks of follow-up was 71% (46-85), but decreased to 0% (-52 to 34) in the last 6 weeks. Vaccination induced strong antibody responses to circumsporozoite protein and strong T-cell responses. Protection was not limited to the NF54 parasite genotype from which the vaccine was derived. 158 men received a fourth dose the next year and were followed up for 9 weeks; during this time, vaccine efficacy was 47% (4-71, p=0.037).

INTERPRETATION:

RTS,S/AS02 is safe, immunogenic, and is the first pre-erythrocytic vaccine to show significant protection against natural P. falciparum infection.

PMID:
11747915
DOI:
10.1016/S0140-6736(01)06957-4
[Indexed for MEDLINE]

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