A polio <e1>outbreak</e1> in Nigeria was caused by the <e2>vaccine</e2> designed to stop it, leaving at least 69 children paralyzed.
A polio outbreak in
A polio outbreak in Nigeria was caused by the vaccine designed to stop it, leaving at least 69 children paralyzed.
<triplet> outbreak <subject> vaccine <object> Cause-Effect(e2,e1)