GlaxoSmithKline’s experimental malaria vaccine cut infections over 18 months in a late-stage study, moving researchers a step closer to making the first protective shot against the disease available as early as 2015.

The RTS,S candidate reduced infections by 46 percent in infants ages 5 months to 17 months, and by 27 percent for 6- to-12-week-old babies in the follow-up period after the first vaccination, the PATH Malaria Vaccine Initiative, which is developing the protection with Glaxo, said in a statement Monday. The trial involved more than 15,000 children in Africa.

Andrew Witty, GSK’s (NYSE: GSK) CEO, hailed the news.

“We’re very encouraged by these latest results, which show that RTS,S continued to provide meaningful protection over 18 months to babies and young children across different regions of Africa,” he said. “While we have 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. These data support our decision to submit a regulatory application for the vaccine candidate which, if successful, would bring us a step closer to having an additional tool to fight this deadly disease. We are grateful to the scientists across Africa and GSK and to our partners who have worked tirelessly for almost 30 years to bring us to this point.”

The vaccine would help cut the fatalities from a disease that afflicts 216 million people annually and kills more than 600,000, mostly children under 5 years old in sub-Saharan Africa, according to the World Health Organization. Glaxo plans to submit the vaccine to the European Medicines Agency for approval next year, and the WHO has said it may in 2015 recommend RTS,S for use if safety and efficacy are satisfactory.

One of the researchers involved in the project said the results were significant.

“In Africa we experience nearly 600,000 deaths annually from malaria, mainly children under five years of age,” said Halidou Tinto, Principal Investigator from the Nanoro, Burkina Faso trial site and chair of the Clinical Trials Partnership Committee. The group oversees the program. “Many millions of malaria cases fill the wards of our hospitals. Progress is being made with bed nets and other measures, but we need more tools to battle this terrible disease.”

RTS,S was more effective in the older group of children. Severe malaria cases were cut by 36 percent and hospitalizations by 42 percent among older infants, the study showed. Reductions for babies weren’t statistically significant.

While the vaccine was less effective compared with results after a one-year follow-up, it remained safe for the study participants, the trial showed.

RTS,S was given in three doses a month apart in this phase III trial. Further data from a 32-month follow-up and the impact of a fourth booster dose given 18 months after the first three shots are expected to be ready next year, according to the statement.

Glaxo has spent more than $350 million on the development of the vaccine so far and expects to invest more than $260 million through completion, the statement showed.

The nonprofit PATH Malaria Vaccine Initiative aims to accelerate development of vaccines against the disease and their availability in endemic countries, and has received more than $200 million from the Bill & Melinda Gates Foundation.

Dr David Kaslow, vice president of product development at PATH, was encouraged by the results but also added a note of caution.

“Given the huge disease burden of malaria among African children, we cannot ignore what these latest results tell us about the potential for RTS,S to have a measurable and significant impact on the health of millions of young children in Africa,” he said. “While we want to be careful about not getting ahead of the data, this trial continues to show that a malaria vaccine could potentially bring an important additional benefit beyond that provided by the tools already in use.”

GSK operates its North American headquarters in RTP.

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