Updated Monday, November 12, 2012 at 02:16 PM
An experimental malaria vaccine, being tested in seven African nations, proved far less effective in stopping the fatal disease in newborns than in older infants, according to the latest results from the study.
The results, announced Friday at a Vaccines for Africa conference in Cape Town, South Africa, showed the vaccine, produced by GlaxoSmithKline (GSK), warded off only about a third of expected infections in babies six to 12 weeks of age.
The years-long trial of the vaccine, the first to be tested against the parasite, is funded by GSK and the PATH Malaria Vaccine Initiative, backed by the Bill & Melinda Gates Foundation.
The first results from the trial, released last year, showed that in 5- to 17-month-old children, the vaccine reduced cases of detectable malaria by 56 percent and severe malaria by 47 percent.
The latest results, published in Friday's New England Journal of Medicine, showed the vaccine was only about 31 percent effective at protecting the youngest babies against detectable malaria and 37 percent against severe malaria.
But the malaria parasite, Plasmodium falciparum, is a wily foe. Those involved in the study said they remained committed to developing the vaccine and were using the data to better understand the discrepancy between the two age groups.
"This is an important scientific milestone and needs more study," Bill Gates said in a statement from the foundation. "The efficacy came back lower than we had hoped, but developing a vaccine against a parasite is a very hard thing to do. The trial is continuing and we look forward to getting more data to determine whether and how to deploy this vaccine."
Dr. John Lusingu, a malaria researcher from Tanzania and one of the trial's principal investigators, said a one-third reduction in infections could save hundreds of thousands of lives. Malaria kills an estimated 655,000 people worldwide, mostly African children, and the economic toll in sub-Saharan Africa is huge.
Researchers have learned that the vaccine is safe, Lusingu said, and does arouse an immune response. They will explore possible explanations for why it didn't work as well in babies, including the possibility that maternal antibodies present in the infant interfered with the vaccine, he said.
Researchers are studying the duration of the protection, as well as possible differences between responses in areas that have high malaria transmission, such as Western Kenya and Burkina Faso and Tanzania, which has relatively low transmission rates, he said.
"Surprises always come from science," he said. "We have a lot to learn within this venture."
Adrian Hill, of Oxford University, who is developing a competing malaria vaccine, noted the study showed the Glaxo vaccine lost its potency after several months.
"The results look bad now, but they will probably be worse later," Hill told The Associated Press.
Hill said the vaccine might be a hard sell, compared to other vaccines like those for meningitis and pneumococcal disease — which are both effective and cheap.
GSK's Mary Anne Rhyne, director of U.S. media relations, said her company remains "fully committed" to developing the vaccine and was encouraged that results showed efficacy and can provide African babies and young children with "meaningful protection" against malaria.
PATH Malaria Vaccine Initiative spokeswoman Sally Ethelston noted that the phase three trial is funded through the end of 2014. "We're all committed to seeing this through and getting the information we need, so the decisions are made on the basis of the evidence," she said.
"We have a couple more years to go before we have all the data in hand. The bottom line is we are learning a lot about how this vaccine works."
In the end, Ethelston said, a vaccine is only one in a "basket of tools," such as bed nets, to combat malaria. "We have never seen it as a silver bullet to replace everything."
Carol M. Ostrom: 206-464-2249 or email@example.com.
On Twitter @costrom.