A new malaria vaccine has the potential to prevent up to 100 million cases of the disease each year and save 200,000 lives, British experts have said.
Eleanor Riley, professor of immunology at the London School of Hygiene and Tropical Medicine, said the RTS,S malaria vaccine could have an "enormous" public health impact, particularly in sub Saharan Africa.
Results released today by British pharmaceutical giant GlaxoSmithKline (GSK) showed the jab continued to protect young children and babies from malaria up to 18 months after vaccination.
The firm now plans to submit an application to European regulators with the hope of getting the vaccine approved - meaning its introduction could be less than two years away.
Over 18 months, the RTS,S vaccine was shown to almost halve the number of malaria cases in children aged five to 17 months.
The study of more than 15,000 babies and young children found the vaccine reduced, by around a quarter, malaria cases in babies aged six to 12 weeks at first vaccination.
The youngsters received the jab in three separate doses one month apart. During follow-up, their immunity to malaria declined and a sample of the children were given a booster jab. Experts are now awaiting results of the booster to see if it offered extended protection.
Prof Riley said the initial three doses had been shown to deliver between 30% and 50% protection.
"In public health terms, if you could vaccinate every child at risk of malaria you could reduce cases by a third to a half and you could reduce deaths by a third to a half," she said. "It would have an enormous impact in terms of public health."
Prof Riley said 200,000 lives a year could be saved worldwide if every at risk child was vaccinated.
And some 100 million cases a year worldwide could be prevented, mostly in sub Saharan Africa.
While it is too early to talk about eradicating the disease entirely, Prof Riley said combining the malaria vaccine with other measures such as spraying homes with insecticides, using insecticide bed nets and improving drugs for treatment would have a huge impact on the numbers affected.
The RTS,S vaccine works by triggering the immune system to defend against the malaria parasite when it first enters the bloodstream and/or when the parasite infects liver cells.
It is designed to prevent the parasite from infecting, maturing and multiplying in the liver.
Prof Riley said the jab prevented 90% to 95% of malaria parasites getting into the bloodstream. But the remaining 5% to 10% of parasites were still enough to make people sick, which is why the jab does not offer complete protection.
Professor Sir Brian Greenwood, from the London School of Hygiene and Tropical Medicine, who is an investigator on the trial, said: "Results show that the malaria vaccine RTS,S/AS01 continues to protect vaccinated children during an 18 month follow-up period, preventing many cases of malaria.
"Protection declined during the follow up period. However, one third of the children in the trial have now received a booster dose of vaccine. We will learn next year if this protects these children for a further period."
Eleven research centres in seven African countries are conducting the trial, together with GSK and the PATH Malaria Vaccine Initiative (MVI), with grant funding from the Bill and Melinda Gates Foundation to MVI.
Sir Andrew Witty, chief executive of GSK, said: "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.
"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."
Dr David Kaslow, vice president of product development at PATH, said: "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.
"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."
The results of the trial were published in Durban, South Africa.
The World Health Organisation (WHO) has indicated a policy recommendation for the RTS,S vaccine could be possible as early as 2015 if it is approved by European regulators.