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Investigational malaria vaccine may be promising
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Forty-five-month follow-up data demonstrated that the investigational malaria vaccine RTS,S/AS02A maintained protection against infection.
Results published by Sacarlal et al in the Journal of Infectious Diseases were presented at the 49th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy by Kathryn Edwards, MD, from Vanderbilt University in Nashville.
The researchers conducted a randomized, controlled, phase 2B trial of the vaccine in 2,022 children aged 1 to 4 years in Mozambique. Results demonstrated that the vaccine was effective against a first or only episode of clinical malaria disease at a rate of 30.5% (95% CI, 18.9%-40.4%). The efficacy against all episodes was 25.6% (95% CI, 11.9-37.1%). The efficacy against severe malaria was 38.3% (95% CI, 3.4-61.3%).
The prevalence of Plasmodium falciparum was 34% lower in the vaccine group than in the control group at the 45-month mark.
“While 30% efficacy is not generally what we like to target for a vaccine, I believe there is reason to hope about this product,” Edwards said. “At all of the definitions of parasitemia, you will see that these efficacy estimates were highly statistically significant when compared between the control and the vaccine group.”
Edwards was asked about the decline in malaria rates among the study population. “It is hard to know why the rates fell, primarily because malaria is somewhat of a moving target,” she said. “We are seeing reductions as a result of the use of bed nets and more effective treatment. However, it is encouraging that over time there was no big rebound among individuals receiving the vaccine. This indicates that the efficacy may stay present.” -by Rob Volansky