An innovative vaccine made from genetic material protected lab animals from the Zika virus in experiments, scientists reported on Thursday, calling it a "promising" lead in fighting the threat to humans.
A single, low dose of the vaccine shielded mice exposed to Zika five months after the shot, they reported in the journal Nature. Monkeys exposed five weeks after they were innoculated were also not affected by the virus.
"We observed rapid and durable protective immunity without adverse events," said senior author Drew Weissman, a professor at the University of Pennsylvania School of Medicine.
"This candidate vaccine represents a promising strategy for the global fight against Zika virus."
Since Zika erupted on a large scale in mid-2015, more than 1.5 million people have been infected, mostly in Brazil and other countries in South America. It is transmitted mainly by mosquitos, but also through sex.
While the virus causes mild, flu-like symptoms in most people, pregnant women run the risk of giving birth to babies with severe brain damage.
The World Health Organisation declared a global health emergency in February last year, and declared it over in mid-November.
Several vaccines for Zika are under development, and a few are in the early phases of human trials. Most vaccines are made from weakened or inert versions of the targeted virus, and seek to trigger a build-up of antibodies to project against full-strength, live virus.
The new vaccine, however, is based on a modified version of genetic material called messenger RNA (mRNA).
Normally the human body would flush out foreign RNA, but the vaccine developed by Weissman's team is designed to pass under the radar of the immune system and enter directly into human cells.
Once there, the vaccine RNA is incorporated into the cell's protein-making machinery, where it mimics the action of a live virus vaccine - building up an immune response.
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