Malaria Vaccine Trial On Babies Shows Promising Results

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Main Category: Immune System / Vaccines
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Article Date: 18 Oct 2007 - 3:00 PST

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An early stage trial carried out in Africa of a malaria vaccine already shown to be effective in adults has suggested it is safe and even more effective for young babies, setting the stage for larger scale final phase trials.

The study is published in the early online edition of The Lancet and was the work of Dr Pedro Alonso, of the Manhica Health Research Centre, in Mozambique, and the Hospital Clinic of the Universitat de Barcelona, Spain, and colleagues.

214 babies in Mozambique participated in the phase I/IIb double blind trial to test safety, immunogenicity, and efficacy of the malaria vaccine, currently referred to by its experimental name RTS,S/AS02D.

The children were randomly assigned to two groups, a vaccine group and a control group. The vaccine group received three doses of RTS,S/AS02D vaccine, and the other received a hepatitis vaccine Energix-B. The doses were given to the babies at age 10, 14 and 18 weeks. The children also received routine immunisations at 8, 12 and 16 weeks of age.

The main object of the trial was to test vaccine safety. This was proven in that there were no serious vaccine-related adverse events in either of the two groups and neither was imbalance found between the two groups in unsolicited adverse events (side effects due to non vaccine causes).

However, the trial also showed good results on vaccine effectiveness because vaccinated babies showed a 65 per cent reduced risk of contracting new malarial infections. This compares with 45 per cent previously reported in a trial involving older children aged between 1 and 4 years.

The authors emphasized that giving children the vaccine was part of a concerted effort to reduce the risk of infection. For example, the children's families were also given free insecticide treated bednets, and their homes were sprayed twice with insecticide against the disease carrying mosquito. The authors wrote:

"The trial was undertaken in an area of high transmission, but in the context of renewed and intense malaria control activities...the future use and deployment of a malaria vaccine should be seen in the context of comprehensive malaria control programmes."

The authors concluded that the trial showed evidence of a strong link betwee the vaccine induced antibodies and the reduction in malarial infection risk. They said that:

"This is of great significance because up until now, immunogenicity was a marker of response with no clearly proven relation to protection, which in turn could only be established with a clinical trial."

They said their findings need to be verified with further trials (this was only a small sample of children), but still provide a strong foothold for the the clinical development of the vaccine.

Another reason to be optimistic about this result is that the vaccine appears to protect against all strains of the malaria parasite, Plasmodium falciparum.

The vaccine works by triggering two arms of the immune system, malarial antibodies and T cells in the liver, which also recognize malaria. The vaccine comprises a protein from the malaria parasite fused onto the surface of hepatitis B virus which the immune system recognizes and attacks.

The vaccine was made by GlaxoSmithKline in partnership with the Path Malaria Vaccine Initiative and the trial was funded by the Bill and Melinda Gates Foundation.

The next stage will be a two year phase III trial which is planned to involve 16,000 children in 7 countries, scheduled to start at the end of 2008.

According to the World Health Organization (WHO), about 40 per cent of the world's population, 2.5 billion people, are at risk of malaria, which mostly strikes those living in the poorest countries. 500 million become severely ill with the disease every year and over 1 million die from it.

In Africa, 1 in every 5 childhood deaths is due to malaria. Every 30 seconds a child dies from malaria, and on average an African child has between 1 and 5 episodes of fever from the disease every year.

"Safety of the RTS,S/AS02D candidate malaria vaccine in infants living in a highly endemic area of Mozambique: a double blind randomised controlled phase I/IIb trial."
John J Aponte, Pedro Aide, Montse Renom, Inacio Mandomando, Quique Bassat, Jahit Sacarlal, M Nelia Manaca, Sarah Lafuente, Arnoldo Barbosa, Amanda Leach, Marc Lievens, Johan Vekemans, Betuel Sigauque, Marie-Claude Dubois, Marie-Ange Demoitié, Marla Sillman, Barbara Savarese, John G McNeil, Eusebio Macete, W Ripley Ballou, Joe Cohen, Pedro L Alonso.
The Lancet Early Online Publication, 17 October 2007.
DOI:10.1016/S0140-6736(07)61542-6

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Written by: Catharine Paddock
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