Malaria vaccine candidate conferred protection in cohort of African children

The RTS,S Clinical Trials Partnership. N Engl J Med. 2011;doi:10.1056/NEJMoa1102287.

Issue: November 2011

The RTS,S/AS01 malaria vaccine was effective against clinical and severe malaria in a study being conducted in seven African countries, according to phase 3 results published online.

The current data are from March 2009 to January. There were 15,460 children from two age categories eligible for the study: aged 6 to 12 weeks and aged 5 to 17 months.

Children were vaccinated with RTS,S/AS01 or a non-malaria comparator vaccine. The primary outcome measure was efficacy against clinical malaria in the 12-month period after vaccination in the first 6,000 children in the older cohort who received all three doses of the vaccine as per protocol, according to the results.

The efficacy of the vaccine was evaluated in both age cohorts after 250 children had an episode of severe malaria.

Fourteen months after the first dose of the vaccine, the incidence of first episodes of clinical malaria in the first 6,000 children in the older cohort was 0.32 episodes/person-year in the study vaccine group and 0.55 episodes/person-year in the control group. The resulting efficacy rates were 50.4% (95% CI, 45.8-54.6) in the intention-to-treat (ITT) population and 55.8% (97.5% CI, 50.6-60.4) in the per-protocol population.

For severe malaria, the efficacy of the vaccine was 45.1% (95% CI, 23.8-60.5) in the ITT population and 47.3% (95% CI, 22.4-64.2) in the per-protocol population.

When the two age groups were combined, the efficacy against severe malaria was 34.8% (95% CI, 16.2-49.2) in the per-protocol population during an average follow-up of 11 months, according to the results.

Adverse event profiles were similar in the two groups. The older children were more likely to have generalized convulsive seizures after vaccination with the study vaccine, with a rate of 1.04/1,000 doses (95% CI, 0.62-1.64).

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