A new malaria vaccine gave 100% protection from the disease to a group of participants in a clinical trial, scientists have said.
Some 67 healthy volunteers who had never had malaria before were given different doses of the drug, called Sanaria PfsPZ-CVac.
Researchers said the best immune response was shown in a group of nine test persons who received the highest dose of the vaccine three times at four-week intervals.
At the end of the trial, all nine of these individuals had 100% protection from the disease.
"That protection was probably caused by specific T-lymphocytes and antibody responses to the parasites in the liver," Professor Peter Kremsner said.
He said researchers analysed the immune reactions and identified protein patterns which will make it possible to further improve malaria vaccines.
Scientists from the University of Tubingen in Germany, in collaboration with the US-based biotech company Sanaria, carried out the clinical trial, with their findings published in the journal Nature.
Malaria parasites are transmitted by the bite of female Anopheles mosquitoes - the Plasmodium falciparum parasite is responsible for most malaria infections and almost all deaths caused by the disease worldwide.
During the trial they injected live malaria parasites into the test subjects, but also added chloroquine, a drug used to treat malaria for years, to prevent the development of the disease.
Once a person is infected, the Plasmodium falciparum parasite migrates to the liver to reproduce - but at this stage a person does not become ill.
Malaria only breaks out when the pathogen leaves the liver, entering the bloodstream and going into the red corpuscles, where it continues to reproduce and spread.
But as soon as the pathogen enters the bloodstream, the scientists said it can be killed by the added chloroquine - and the disease cannot break out.
"By vaccinating with a live, fully active pathogen, it seems clear that we were able to set off a very strong immune response," said Dr Benjamin Mordmueller.
"Additionally, all the data we have so far indicate that what we have here is relatively stable, long-lasting protection."
Of the group who showed 100% protection after receiving a high dose three times, the protection was still in place after 10 weeks and remained measurable for even longer, Dr Mordmueller said.
He said the new vaccine showed no adverse effects on those it was tested on and that the next step is to further test the vaccine's effectiveness over several years in a clinical study in Gabon.
Malaria is one of the deadliest infectious diseases in the world and the search for a vaccine has been going on for more than a century.
According to the World Health Organisation, 214 million people became infected with malaria in 2015 alone - with an estimated death toll of 438,000.
The vast majority of cases were in Africa, where around 90% of the deaths occurred.
Almost three-quarters of those who succumb to the disease are children under five.