US researchers announced their success on Thursday in the journal Science, explaining the results of a small, early-stage clinical trial.

"This was something that everybody said was not possible. And here it is," Navy Captain Judith Epstein, one of the researchers, told the Reuters news agency.

"We’re in the first stages now of really being able to have a completely effective vaccine," she said.

Trial a success

The vaccine was produced by Sanaria Inc of Maryland, and the clinical trial was conducted between October 2011 and October 2012.

Participants, both those who got the vaccine and those who didn’t, were exposed to bites from five malaria-infected mosquitoes. The study showed that those who got higher doses of the vaccine were far less likely to develop the disease.

The results of the trial, according to Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), were the most promising yet of any experimental vaccine.

Hopeful but not certain

He stopped short of calling it a breakthrough, noting that only a small number of people were involved in the trial. There were 57 healthy participants in the study.

Fauci also pointed out that it is unclear how long the vaccine’s protection against malaria lasts.

The PfSPZ vaccine is made from live but weakened parasites of the species Plasmodium falciparum, the most deadly of the malaria-causing parasites.

A great deal more work needs to be done before the vaccine is set in motion for public use, but the early results are looking good.

"There are several more steps before you can feel comfortable that you have something that might be ready for prime time," Fauci explained. "So we're really not there yet, but it’s encouraging to see these very favorable results."

Sanaria's chief scientific officer, Stephen Hoffman, who co-authored the study with Robert Seder of the NIAID, estimates that it will be four years before the vaccine will be publicly available.

At the moment, there is no vaccine on the market for malaria.

tm/ccp (AFP, Reuters)