A new kind of malaria vaccine that mimics the effect of mosquito bites has shown early promise by offering 100 percent protection to a dozen human volunteers, researchers said Thursday.
The experimental vaccine, called PfSPZ and produced by the Maryland-based company Sanaria, contains live malaria parasites collected through a painstaking process of dissecting the salivary glands of mosquitoes.
These immature parasites, known as sporozoites, are then weakened so they cannot cause illness and incorporated into a vaccine, which must be injected into a person's veins several times, with each shot about a month apart.
"When we started doing this, everybody knew that sporozoites were the gold standard but everyone thought it was impossible to make a vaccine out of sporozoites and we were crazy. And we have proven them wrong," Sanaria chief scientific officer Stephen Hoffman told AFP.
A test two years ago that administered the same vaccine into the skin of patients, the way most vaccines are given, protected only two of 44 volunteers.
But the latest trial showed that injecting the vaccine into the bloodstream protected against malaria in all six volunteers who received a five-shot regimen at the highest dosage, according to the results published in the US journal Science.
Six of nine volunteers in a separate group that received four shots of the highest dose -- 135,000 sporozoites per injection -- were also fully protected against malaria, it said.
The phase I study included 57 people -- including 40 who received the vaccine in varying doses and 17 controls.
The study was co-authored by Hoffman and Robert Seder of the National Institute of Allergy and Infectious Diseases.
"The good news is that the proof of concept is quite impressive," said Anthony Fauci, director of NIAID.
"The sobering news is that we that we still have a lot of work to do in order to prove that this is something that has very broad applications."
Hoffman estimated it would be four years before a vaccine may reach the marketplace. He said about $110 million has been invested so far.
"The major challenge has been overcome -- that is to prove the principle that we actually have a product that can protect all the people whom we immunize."
Sanaria is also teaming with Harvard University engineers to automate the process of dissecting the mosquitoes.
The company currently employs 16 "dissectors" who can each tease apart about 150 mosquitoes an hour, Hoffman told AFP.
According to Regina Rabinovich, a malaria expert and scholar in residence at Harvard University, the results are "encouraging."
However, she said the researchers "need to figure out how to replicate with a scalable technology."