GSK malaria vaccine found to be less effective over time

Hannah Blake

pharmaphorum

New clinical trial data shows that the effectiveness of GlaxoSmithKline’s malaria vaccine decreases over time, with the vaccine protecting only 16.8% of children over four years.

Phase 3 clinical trials of RTS,S followed children who had been randomly assigned, at 5 to 17 months of age, to receive three doses of RTS,S/AS01E vaccine (223 children) or rabies vaccine (224 controls) over four years. The end point was clinical malaria (temperature of ?37.5°C and Plasmodium falciparum parasitemia density of &gt,2500 parasites per cubic millimeter).

Researchers from KEMRI-Wellcome Trust Research Programme and Oxford University in Kenya ran the trials, which found that the efficacy of the candidate RTS,S vaccine dropped from 43.6% protection against malaria in the first year, to zero by the fourth year after vaccination.

These disappointing results were published in the New England Journal of Medicine (NEJM) this week.

However, researchers believe there is still a clear benefit to the vaccine candidate.

“Despite waning efficacy over time and with a higher level of exposure to malaria, vaccination with RTS,S/AS01E resulted in an overall reduction in the number of episodes of clinical malaria over a 4-year follow-up period, in total, 65 cases were averted per 100 vaccinated children.”

Extract from page 1120 of the March 21, 2013 Vol. 368 No. 12 NEJM.

GSK's RTS,S is the most advanced candidate malaria vaccine in development. Full data from final-stage trials involving over 15,000 children are expected by the end of 2013.