Large-scale trials of Zika vaccines could take 18 months: WHO

Geneva

An estimated 15 companies or groups have begun work on a vaccine for the previously obscure virus which has now become a global concern, WHO's deputy director for health systems and innovation Marie-Paule Kieny told journalists.

There are currently two candidates which appear most promising, including one vaccine being developed by the US National Institutes of Health and another from India based Bharat Biotech, Kieny said.

"In spite of this encouraging landscape, vaccines are at least 18 months away from large-scale trials," she added.

Meanwhile, Kieny said it would take an estimated "few weeks" to establish whether Zika causes microcephaly and the severe neurological disorder Guillain-Barre syndrome.

While most people infected with Zika have only mild symptoms, rising anxiety about the virus is driven by its strongly suspected link to the two more serious conditions.

Microcephaly can cause babies to be born with abnormally small heads and brains, while Guillain-Barre can cause paralysis or even death.

WHO has said Zika's link with microcephaly was "strongly suspected," while Kieny told journalists Friday that the causal relationship with Guillain-Barre was "highly probable."

"I think the evidence is building on the causal link," she added, explaining that an ongoing trial among pregnant woman in Colombia was expected to yield new evidence soon.

Zika, which is carried by mosquitos, has spread rapidly through Latin America and the Caribbean, with multiple governments in the most affected areas urging women to avoid getting pregnant for the time being.

Brazil, the hardest hit country, has recorded 1.5 million Zika cases since early 2015 and concern is mounting about the potential dangers of hosting this summer's Olympic Games in Rio de Janeiro.

While a usable vaccine remains a priority, Kieny said that advances in testing were also urgently needed.

She said an estimated 20 companies were at various stages of development for a range of diagnostic methods and that rapid testing systems which can be particularly useful in more remote areas were a priority.