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Pediatric Malaria Vaccine Efficacy Declines With Time

Dose is effective in reducing clinical episodes, but effect drops off during follow-up period

Pediatric Malaria Vaccine Efficacy Declines With Time

WEDNESDAY, March 20 (HealthDay News) -- A pediatric malaria vaccine reduces episodes of clinical malaria but its efficacy declines over time, according to a study in the March 21 issue of The New England Journal of Medicine.

Ally Olotu, M.B., Ch.B., from the Kenya Medical Research Institute-Wellcome Trust Research Programme in Kilifi, and colleagues analyzed data four years after the third dose was administered to 447 children 5 to 17 months old in Kilifi who had been randomly assigned to the RTS,S/AS01E malaria vaccine or rabies vaccine.

The researchers found that for first or only episodes of clinical malaria, vaccine efficacy was 29.9 percent in the intention-to-treat analysis and 32.1 percent in the per-protocol analysis. For multiple episodes, vaccine efficacy was 16.8 percent in the intention-to-treat analysis and 24.3 percent in the per-protocol analysis. Overall, 65 cases of clinical malaria were averted for every 100 vaccinated children. Vaccine efficacy declined from 43.6 percent in the first year to −0.4 percent in the fourth year. Vaccine efficacy was 45.1 percent for children with low or average malaria exposure but only 15.9 percent for children with high malaria exposure.

"In conclusion, RTS,S/AS01E was associated with a reduction in the incidence of first and of all episodes of Plasmodium falciparum clinical malaria, but vaccine efficacy waned during the four years of follow-up," the authors write.

The original study was sponsored by GlaxoSmithKline Biologicals; two authors are employees of the company.

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