The World Health Organisation on Friday said that large-scale trials for the Zika virus vaccine are at least 18 months away. WHO’s deputy director for health systems and innovation, Marie-Paule Kieny, said that around 15 companies or groups have begun work on a vaccine out of which two candidates appear most promising: one from the United States’ National Institutes of Health and another from Bharat Biotech in India.

Kieny also told AFP that it would take four to eight weeks to establish whether Zika causes microcephaly and the severe neurological disorder Guillain-Barre syndrome. Microcephaly can cause babies to be born with abnormally small heads and brains, while Guillain-Barre can cause paralysis or even death.

The WHO recently declared an international health emergency after an outbreak of Zika in Latin America. Brazil alone has registered around 4,000 cases of babies suffering from microcephaly and warned pregnant women to stay away from the 2016 Olympics that begin in August.