Promising results for malaria vaccine

December 06, 2001

N.B. Please note that if you are outside North America the embargo for Lancet Press Material is 0001 hours UK Time Friday 7th December 2001.

Results of a study from The Gambia in this week's issue of THE LANCET provide evidence of a vaccine that could prevent malaria caused by the micro-organism Plasmodium falciparum.

P. falciparum malaria remains a major cause of disease and death in many parts of the tropics, especially in sub-Saharan Africa. The development of an effective vaccine is a major health priority for these countries. Current research is focused on developing pre-erythrocytic vaccines, which prevent infection of the red blood cells (erythrocytes), the stage at which the disease leads to the development of serious symptoms. Kalifa Bojang and colleagues from the UK Medical Research Council Laboratories in The Gambia did a randomised trial to assess the effectiveness of the pre-erythrocytic malaria vaccine RTS,S/AS02 against natural P. falciparum infection in semi-immune adult men in The Gambia.

306 men were randomly assigned three doses of either RTS,S/AS02 (the treatment group) or rabies vaccine (the control group). 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 the time to the first infection with P. falciparum.

250 men (131 in the treatment group and 119 in the control group) received three doses of vaccine and were followed up for 15 weeks. P. falciparum infections occurred significantly earlier in the control group than the treatment group. The overall malaria vaccine efficacy was 34%. 158 men received a fourth dose the next year and were followed up for 9 weeks; during this time, vaccine effectiveness was 47%. It is not known if the booster dose was needed to prolong protection. There was an indication in the first year of the trial that efficacy was higher at first and started to wane. The investigators conclude that RTS,S/AS02 is safe and is the first pre-erythrocytic vaccine to show significant protection against natural P. falciparum infection.
Contact: Dr Kalifa Bojang, MRC Laboratories - The Gambia, PO Box 273, Banjul, The Gambia; T) +220 495 442; F) +220 496 513; E)


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