Scientists in the US believe they have found not one, but two vaccines that can provide complete protection from the Zika virus.
They say human trials could start by the end of the year, after being successfully carried out on mice, bringing them yet another step closer to finding an effective vaccine for people.
Experts at the Beth Israel Deaconess Medical Centre – part of Harvard Medical School, the Walter Reed Army Institute of Research (WRAIR) and the University of Sao Paulo – found that mice given either of two jabs did not pick up Zika when they were exposed to it up to two months later.
One of the jabs was a DNA vaccine based on a Zika virus strain isolated in Brazil, while the other was a purified, inactivated virus vaccine (meaning it was made non-functional) based on a Zika virus strain isolated in Puerto Rico.
The study, published in the journal Nature, showed that single shots of either vaccine completely protected the mice against Zika.
Colonel Stephen Thomas, an infectious disease army doctor and head of the Zika vaccine programme at WRAIR, said the institute could now develop a proper vaccine that builds on a type of vaccine that has been licensed before – and he is confident it will work.
He said: “This critical first step has informed our ongoing work in non-human primates and gives us early confidence that development of a protective Zika virus vaccine for humans is feasible.”
But it won’t be a simple transition from finding an effective vaccine for mice to developing one that will work for humans.
Jonathan Ball, professor of molecular virology at the University of Nottingham, said: “On the face of it, this is very good news and a significant step towards developing an effective vaccine to prevent Zika virus infection and the horrendous complications that this virus can sometimes cause.
“But we have to take these data in context, these were mice experiments and there is a long way to go before you can be sure that this vaccine candidate will perform in humans.”
The World Health Organisation (WHO) has declared Zika a global public health emergency and has warned it could spread to European holiday destinations this summer.
Zika is spread by mosquitoes and causes severe brain defects in unborn children. It is also linked to the neurological condition Guillain-Barre syndrome.