London, Oct 8 (Reuters): British drugmaker GlaxoSmithKline will seek marketing approval for the world's first malaria vaccine next year after trial data showed the shot significantly cut cases of the disease in African children.

The vaccine known as RTS,S was found, after 18 months of follow-up, to have almost halved the number of malaria cases in young children in the trial, and to have reduced by around a quarter the number of malaria cases in infants.

"Based on these data, GSK now intends to submit, in 2014, a regulatory application to the European Medicines Agency (EMA)," GSK, which has been developing the vaccine for three decades, said in a statement.

It added that the United Nations health agency, the Geneva-based World Health Organization (WHO), has indicated it may recommend use of the RTS,S vaccine from as early as 2015 if EMA drugs regulators back its licence application.

Malaria, a mosquito-borne parasitic disease, kills hundreds of thousands of people a year, mainly babies in the poorest parts of sub-Saharan Africa, and scientists say an effective vaccine is key to attempts to eradicate it.

Yet hopes that RTS,S would be the final answer were dampened last year when results from a final-stage trial with 6,537 babies aged six to 12 weeks showed the shot provided only modest protection, reducing episodes of the disease by 30 percent compared to immunisation with a control vaccine.

Malaria Cases Fill Hospital Wards

Tuesday's latest readout from the malaria trial, which is Africa's largest ever clinical trial involving almost 15,500 children in seven countries, were presented at a medical meeting in Durban, South Africa.

GSK is developing RTS,S with the non-profit PATH Malaria Vaccine Initiative (MVI), with grant funding from the Bill & Melinda Gates Foundation to MVI.

"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," said Halidou Tinto, a lead investigator on the RTS,S trial from Burkina Faso.

Previous data sets released from earlier parts of the trial showed the vaccine's efficacy was 65 percent in babies analysed six months after vaccination, and only around 50 percent in five to 17 month-olds.

And further data released earlier this year found RTS,S's effectiveness wanes over time, with the shot protecting only 16.8 percent of children over four years.

Despite these drawbacks, David Kaslow, vice president of product development at PATH, said RTS,S would serve as a useful additional tool alongside other malaria control measures such as mosquito nets, insecticides and anti-malaria drugs.

"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 in a statement.

"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."

If approved, the vaccine is unlikely to be anything other than neutral for GSK's bottom line. GSK has promised that if RTS,S is given the market go-ahead, it will be priced at cost of manufacture plus a 5 percent margin, and the margin would be reinvested in malaria research.