Passage Summary: Scientists have a new chicken pox drug that works well and has no side effects, yet they say it might be dangerous if everyone starts using it.

Reasoning: No reasoning (Fact Set).

Analysis: The paradox here lies in the contradiction between the drug's individual safety and its collective danger. We need to find a piece of information that explains why 'widespread use' creates a risk that doesn't exist on an individual level. Perhaps the drug prevents natural long-term immunity, leading to more dangerous outbreaks in adults, or maybe it encourages the virus to evolve into a more resistant strain. Look for an answer that addresses the negative consequences of the drug being used by the general population rather than just one person.