Results from the largest and longest trial of a malaria vaccine were announced Tuesday at a conference in Durban, South Africa. The vaccine, called RTS,S, was tested on 15,000 children at 11 sites in seven African countries.
Scientists hope to have the world’s first malaria vaccine approved by 2015 and in use by 2016.
“It’s on that trajectory, and the plan is to file with the European Medicines Agency in 2014,” said David Kaslow, VP of product development at the PATH Malaria Vaccine Initiative, which supported development of the vaccine.
Previous data, at the one year mark, showed 56 percent fewer cases of malaria in toddlers aged 5 – 17 months and 31 percent fewer cases in babies aged 6 – 12 weeks.
Eighteen months into the trial, new data shows the vaccine’s efficiency has waned slightly, with 46 percent fewer cases of malaria in the older group of children, and 27 percent fewer cases in the younger group.
“We expected this,” said Kaslow. “Efficacy wanes for most vaccines, which is why, for example, we give booster shots for tetanus.”
“One-third of the children in the trial have now received a booster dose, so we’ll learn in the next year if this protects the children for a further period,” said Brian Greenwood of the London School of Hygiene and Tropical Medicine.
The older age group will be followed for a total of 41 months, but the newest results are encouraging enough to persuade the vaccine’s maker, GlaxoSmithKline (GSK), to submit it for approval.
“While we’ve seen some decline in vaccine efficacy over time, the sheer number of children affected by malaria means that the number of cases of the disease the vaccine can help prevent is impressive,” says Andrew Witty, CEO of GSK.
Researchers estimate the vaccine has the potential to prevent 941 cases of malaria per 1000 children vaccinated in the older age group, and 444 among vaccinated babies.
Kaslow said there is no explanation as to why the vaccine appears to be more effective in older children, but there are three possible reasons. One is that babies’ immune systems are not mature enough to respond to the vaccine. Unlike the older children, the babies received a pentavalent vaccine at the same time to fight against five other diseases.
“It’s possible the hepatits B component of the pentavalent vaccine interfered with the malaria vaccine, but we don’t know yet,” he says.
Lastly, there could be some interference from maternal antibodies.
According to Kaslow, there is also hope for a cure from other vaccinations entering trials, particularly those for “transmission-blocking” vaccines.
More than 200 million people are infected with malaria every year. The disease kills at least 660,000 people, most of whom are children.