A clinical trial of GlaxoSmithKline's experimental malaria vaccine RTS,S/AS02A conducted among 214 infants in Mozambique has shown that the vaccine is safe and can reduce the number of new cases by 65% after a three-dose course, according to a study published online on Wednesday in the Lancet, the New York Times reports. The vaccine is produced by merging a section of outer protein from the Plasmodium malaria parasite with hepatitis B and a chemical booster. The booster and hepatitis B segment are added to induce a stronger immune system response, according to the Times (McNeil, New York Times, 10/18).

Lead researcher Pedro Alonso of the University of Barcelona and colleagues provided the vaccine to half of the infants at ages 10, 14 and 18 weeks. The control group received a hepatitis B vaccine (Maugh, Los Angeles Times, 10/18). The Phase II trial was conducted in conjunction with scientists from the Manhica Health Research Center and the Mozambique Ministry of Health (GSK release, 10/17).

The study was conducted primarily to test the safety of the vaccine, and the researchers recorded no adverse side effects associated with RTS,S. They also recorded 65% fewer new malaria cases and clinical illnesses among the infants who received the full three doses of the vaccine following the final dose, compared with the infants in the control group. In some cases, infants contracted malaria before receiving a full course of treatment, but the researchers found that even infants who received one dose of the vaccine had a 35% reduced risk of illness during the first six months of the study (Los Angeles Times, 10/18).

It is not known how long protection from the vaccine will last, according to the New York Times. However, because infants are the most vulnerable to malaria, the vaccine gives them time to develop natural immunity to the disease, according to Alonso (New York Times, 10/18). In addition to the vaccine, all of the infants' families were given no-cost insecticide-treated nets, and their homes were sprayed with insecticide twice (Whalen, Wall Street Journal, 10/18).

Although RTS,S offers a lower level of protection compared with the standard level of around 80% to 90% provided by most other vaccines, malaria experts say that even this amount of protection could be significant, according to the Seattle Post-Intelligencer. "You need to factor into this the burden of disease," Alonso said, adding that a "vaccine that provides moderate efficacy could have a very significant public health impact" (Paulson, Seattle Post-Intelligencer, 10/17). According to the New York Times, the vaccine's three-dose regimen could be an "obstacle in poor countries," some of which have difficulty giving oral vaccine for diseases such as polio (New York Times, 10/18).

A larger trial of the vaccine that will include 16,000 children in seven African countries is scheduled to begin in 2008 (Los Angeles Times, 10/18). If the vaccine passes that trial and if national regulatory agencies accept it, RTS,S -- which likely will be given the brand name Mosquirix -- could be ready for distribution by 2012, Ripley Ballou, GSK's vice president for international clinical trials, said (New York Times, 10/18). The drug maker has spent $300 million to develop the vaccine to date and expects to spend an additional $50 million to $100 million to bring it to market, according to Ballou (Los Angeles Times, 10/18). About $100 million has been provided by the Bill & Melinda Gates Foundation through the PATH Malaria Vaccine Initiative. It is unclear what the cost of the vaccine will be, but if a "child will benefit, price will not stand in the way," Christian Loucq, director of MVI, said (New York Times, 10/18). The study was presented on Wednesday at a malaria forum hosted by the Gates Foundation in Seattle (Los Angeles Times, 10/18).

The study is available online.

Webcasts of select Gates Foundation forum sessions are available online at kaisernetwork.org