GlaxoSmithKline Malaria Vaccine Safe and Effective

LONDON (Reuters Health) Dec 06 - RTS,S/AS02 (GlaxoSmithKline Biologicals, Rixensart, Belgium) is the first pre-erythrocytic malaria vaccine to offer significant protection for semi-immune adults exposed to natural infection, according to results from a randomized trial conducted in The Gambia. The vaccine targets Plasmodium falciparum before the parasites reach the stage that causes disease.

In the December 8th issue of The Lancet, Dr. Kalifa Bojang from the Medical Research Council Laboratories, Banjul, and colleagues present data on 250 men who received three doses of RTS,S/AS02 or rabies vaccine at the start of the malaria transmission season. The subjects were followed for 15 weeks.

During follow-up the control group developed P. falciparum infections significantly earlier than those given RTS,S/AS02 (p = 0.018), the research team reports. After adjustment for confounders, the efficacy of the malaria vaccine was 34% (p = 0.014).

In the first 9 weeks of follow-up estimated RTS,S/AS02 efficacy was 71%, but it dropped to 0% in the last 6 weeks of follow-up, Dr. Bojang's group calculated. RTS,S/AS02 was safe and well tolerated.

The vaccine induced a strong T-cell response and a strong antibody response to circumsporozoite protein. Protection derived from RTS,S/AS02 was not limited to the NF54 parasite genotype from which the vaccine was created, the investigators found.

In the following year 158 of the men were given a fourth dose of RTS,S/AS02 and were followed for 9 weeks. During this follow-up RTS,S/AS02 efficacy was 47% (p = 0.37), Dr. Bojang's team found.

"Studies to assess the usefulness of this vaccine in children are planned and various means of improving protection with better adjuvant formulations, prime-boost immunisation strategies, or additional antigens will be pursued," the authors say.

Lancet 2001;358:1927-1934.