Zika has hit Florida. At least 14 cases of infection with the mosquito-borne virus are now confirmed, with more certain to come, and federal health officials are warning against visiting the Miami neighborhood where transmission occurred. Meanwhile, top athletes in golf and cycling, citing reluctance to travel to a Zika-afflicted area, have opted out of the Rio Olympic Games that begin in Brazil on Friday.

Federal health officials have been touting the rapid progress in developing a Zika vaccine to protect against the virus,...