Malaria vaccine proving promising

Researchers investigating an experimental malaria immunization are moving it into a large phase III trial in response to recent positive results.

"We are closer than ever before to having a malaria vaccine," said Dr. Christian Loucq, director of the PATH Malaria Vaccine Initiative. "The world urgently needs a safe and effective vaccine. Even a partially effective vaccine has the potential to save hundreds of thousands of lives each year."

Data from phase II projects investigating the RTS,S/AS01E and the RTS,S/AS02D malaria vaccines were published in the Dec. 11, 2008, New England Journal of Medicine and presented at last month's American Society of Tropical Medicine and Hygiene meeting in New Orleans.

These two-shot formulas contain the same antigen but have different adjuvants.

One study randomized 894 infants and toddlers in Kenya and Tanzania to receive either RTS,S/AS01E or rabies shots. The RTS,S/AS01E vaccine reduced the incidence of illness caused by the malaria parasite by 53% over eight months. Those receiving the investigation product also experienced fewer serious adverse events than did those who received the rabies vaccine.

A second study randomized 340 infants in Tanzania to receive either three doses of RTS,S/AS02D or the hepatitis B vaccination, in conjunction with the usual immunization schedule. The RTS,S/AS02D vaccine reduced the risk of being infected with the malaria parasite by slightly more than 65% over a six-month period. Also, it did not interfere with the effect of the other vaccines.

"These results are very exciting and give me renewed hope of having a malaria vaccine in the not-too-distant future," said Dr. Salim Abdulla, lead author on the second paper and head of the Bagamoyo Branch of the Ifakara Health Institute in Bagamoyo, Tanzania.

Multicenter phase III efficacy trials are expected to start early this year, pending approval by national regulatory agencies and ethics committees.