Final clinical trials of the world's first vaccine for malaria suggest it has the "potential to prevent millions of cases", researchers have said.
In a report published in the Lancet medical journal, scientists found the drug could make a "substantial contribution" to controlling malaria, which kills hundreds of thousands every year.
Tests on around 15,500 toddlers and babies in seven sub-Saharan African countries suggested the vaccine, named RTS,S, was around 36% effective for children aged between five and 17 months.
But the trials also found the vaccine was not as effective in younger children and protection wanes over time.
The study's author Professor Brian Greenwood, of the London School of Hygiene and Tropical Medicine, told ITV News: "We really do want a malaria vaccine that is more effective than that but this is the first one".
Researchers are optimistic the results would allow the European Medicines Agency along with the World Health Organisation (WHO), to reach a "positive opinion".
The report said: "The results provided in this phase three trial should help these groups in making their decisions and, if RTS,S is licenced in African countries, help national malaria control programmes in deciding how best to use this vaccine, which, if used correctly, has the potential to prevent millions of cases of malaria."
The drug has been co-developed by GlaxoSmithKline and the non-profit PATH Malaria Vaccine Initiative, which received $156m (£102m) funding from the Bill & Melinda Gates Foundation.
The latest WHO figures show there were about 198 million cases of malaria in 2013 and an estimated 584,000 deaths.
Most fatalities occur among children living in Africa, where a child dies every minute from malaria.