A new malaria drug gave 100% protection to participants involved in a clinical vaccine trial, according to scientists.
Some 67 volunteers put themselves forward to be given doses of Sanaria PfsPZ-CV in an attempt to safeguard against the mosquito-borne disease.
Nine of the participants who received the highest dose of the drug at four-week intervals displayed the best immune response, affording them 100% protection.
The findings, published in the journal Nature, indicated that protection was likely caused by specific T-lymphocytes and antibody responses to parasites in the liver.
Researchers analysed the immune reactions and identified protein patterns which, they hope, will make it possible to further improve malaria vaccines.
One of the deadliest infectious diseases in the world, a search for a vaccine against malaria - which infected 214 million people in 2015 alone - has been going on for over a century.
The death toll last year from the disease was 483,000.
Malaria parasites are transmitted by the bite of female Anopheles mosquitoes - the Plasmodium falciparum parasite being responsible for most malaria infections and almost all deaths caused by the disease worldwide.
During the trial, injected live malaria parasites were injected into volunteers, 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, scientists say, 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," Dr Benjamin Mordmueller said.
"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 added.
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.