BioEd Online

The world's most advanced malaria vaccine entered its final phase of pre-approval testing yesterday in Bagamoyo, Tanzania, raising hopes that the drug could be licensed for widespread use by 2012.

On 26 May, five infants aged 5–17 months were inoculated with GlaxoSmithKline (GSK)'s RTS,S vaccine. In the coming months, the study will become the largest ever trial of a malaria vaccine candidate, involving 16,000 children under the age of two at eleven sites in seven African countries.

Investigators hope that the phase III trials will show that RTS,S prevents at least half of the infants and young children who are vaccinated from developing the symptoms of malaria, and that the protection will last for several years. Even a partially effective vaccine is sorely needed. Most of the one million people killed every year by malaria are children under the age of 5 in sub-Saharan Africa, the World Health Organization says.

"This vaccine has the potential to save hundreds of thousands of lives," says Salim Abdulla, principal investigator of the Tanzanian trial. "It's an amazing feeling to be a part of [this trial]."

Long, long road

It has taken researchers more than two decades to nurture RTS,S through to its third phase — the final stage of development before the drug is sent for regulatory approval. GSK and its partner, the Malaria Vaccine Initiative which is funded through the Bill & Melinda Gates Foundation, say they have invested more than US$400 million in the project.

The drug is a combination vaccine, which fuses fragments of a protein from the malaria parasite with a surface antigen from the hepatitis B virus. "Several other approaches have shown scientific promise," says Vasee Moorthy, a medical officer who works on malaria vaccines at the World Health Organization's Initiative for Vaccine Research. But only RTS,S has reached phase III trials.

After promising safety and efficacy trials that involved a few thousand children, phase III trials had been scheduled for April 2009 in Lambaréné, Gabon. But the country's newly appointed minister of health, Idriss Ngari, requested more time to review documents before finalizing his decision, explains Christian Loucq, director of the Malaria Vaccine Initiative.

If all goes well, the vaccine could be submitted for regulatory review by 2011 and on the market by 2012. The Malaria Vaccine Initiative says it is working with organizations that fund vaccines, such as the Global Fund to Fight AIDS, Tuberculosis and Malaria and the Global Alliance for Vaccine and Immunizations, to ensure that RTS,S will be affordable if it reaches the market.

"The cost to African babies and mothers is going to be nil," says Loucq. "That is very clear."