The leading malaria vaccine candidate has shown disappointing results, the final study showing that in many cases it simply doesn't work very well and that the initial protection fades with time. Despite these results, it has protected about one third of the children vaccinated and developers of the drug are moving ahead to get it approved because it could still help protect some children from contracting the mosquito spread disease.
GlaxoSmithKline has spent hundreds of millions of dollars to develop the vaccine, which will likely end up being the worlds first licensed shot for malaria once the European Medicines Agency reaches its decision later this year.
The World Health Organization had previously set a target of 2015 for having a malaria vaccine that was at least 50 percent effective with protection lasting longer than a year. According to a study published in the journal The Lancet, those goals have been missed with this vaccine, though scientists believe it has not been a complete waste.
"Everyone accepts that this is not the perfect or the last malaria vaccine," said Brian Greenwood of the London School of Hygiene and Tropical Medicine, the study's lead author. "It's not good enough to stop transmission but it will cut the huge burden of disease."
He noted there are about 200 million cases of malaria every year, with many children infected multiple times.
"Preventing some of those attacks is not insignificant," Greenwood says. The vaccine study involved about 15,500 babies and toddlers in Africa; one group got three doses; a second group also got a booster shot and a third group got dummy shots. All of the children used a mosquito bed net and they were followed for up to four years.
Overall, the vaccine was about 30 percent effective in those who got three doses and a booster but the protection faded over time. It did, however, work better in those that were 5 to 17 months in age with a rate of effectiveness of about 36 percent. But it was only 26 effective in babies and the vaccination made no difference in severe malaria rates or deaths.
If you compare these statistics to other vaccines such as those for measles and polio, the results are very disheartening. These types of vaccines work more than 90 percent of the time showing that the malaria vaccine was far short of the goal.
WHO estimates that malaria killed more than 580,000 people in 2013 with children under the age of 5 in Africa being the most frequent victims. Officials try to slow the mosquitoes by using bed nets, insecticides, and giving out malaria medications to entire villages that are more at risk.
"This vaccine could mean children will have only two bouts of malaria a year instead of five," said Dr. Martin De Smet, a malaria expert at Doctors Without Borders, who was not connected to the study.
He said convincing parents to get their children vaccinated several times might be a tough sell. "They know their child will probably get some malaria despite the vaccination, so how enthusiastic are they going to be?"
Not everyone agrees however. Adrian Hill of Oxford University, who is working on a rival malaria vaccine said that it was worrying that children who got three doses but didn't get a booster appeared to be more vulnerable to malaria afterward.
"The vaccine stops them from building up natural immunity to malaria, so then when the protection wears off, they may be more susceptible," he said.
He did agree, however, that the vaccine would most likely be useful in certain situations, and some scientists are adding other components to the vaccine to make it more potent. WHO is expected to make its recommendation about the vaccine in October if the European Medicines Agency has issued its assessment by then.
