GENEVA (AP) — Possible Zika vaccines are at least 18 months away from large-scale trials, the World Health Organization said Friday, while advising pregnant women to consider delaying travel to areas where the mosquito-borne virus has turned up amid concerns it may be linked to abnormally small heads in newborn children. Marie-Paule Kieny, WHO assistant director-general for health systems and innovation, says the U.N.