NEW YORK (Reuters Health) - The results of a phase IIb proof-of-concept efficacy trial in children show that the malaria vaccine RTS,S/AS02A is safe, well tolerated, and immunogenic. The vaccine was effective in reducing the prevalence of Plasmodium falciparum parasitemia and in preventing clinical episodes of disease, according to a report in the October 16th issue of The Lancet.
A previous randomized, controlled trial of GlaxoSmithKline’s RTS,S/AS02A showed it to be effective in protecting against natural infection (see Reuters Health report, December 6, 2001).
In the current trial involving two different Mozambique-based cohorts of children between 1 and 4 years old, Dr. Pedro L. Alonso, at Universitat de Barcelona in Spain, and colleagues examined the efficacy of the vaccine “at two points in the life cycle and pathogenesis of malaria: infection and clinical disease.”
In cohort 1, 803 subjects were randomized to three doses of RTS,S/AS02A and 802 were assigned to control vaccines. Vaccine efficacy was adjusted for age, bednet use, geographical area and distance from a health center.
A first clinical episode during 6 months after the third dose occurred in 123 of those in the RTS,S/AS02A group and in 159 in the control group (29.9% efficacy, p = 0.004). Prevalence of parasitemia was 11.9% and 18.9%, respectively (37% reduction, p = 0.0003). Vaccine efficacy for severe malaria was 57.7% (p = 0.019).
In the second cohort, 209 received RTS,S/AS02A and 208 received control vaccines. RTS,S/AS02A was 45% effective in extending time to first infection with P. falciparum (157 in the vaccine group and 166 in the control group, p < 0.0001).
“Children who received RTS,S/AS02A had fewer all-cause serious adverse events, admissions, and severe complications from malaria than did those in the control group,” Dr. Alonso’s group writes.
“The road toward a safe and efficient malaria vaccine being available and useable on a large scale, or even incorporated into an expanded program of immunisation, will be long and chaotic,” Drs. Philippe Van de Perre and Jean-Pierre Dedet, of University of Montpellier in France, write in an accompanying editorial.
“Thus for many decades ahead, the expansion of preventive and therapeutic strategies, including those new ones with an evident added value (eg., insecticide-impregnated bed nets and treatment with artemisinin-containing regimens) should remain an utmost priority to stop the malaria hecatomb,” they conclude.
Source: Lancet 2004;364:1380-1383,1411-1420. [ Google search on this article ]
MeSH Headings:Recombinant Proteins: Vaccines, Synthetic: Protozoan Vaccines: Malaria VaccinesCopyright © 2002 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.
