If you have never been exposed to the varicella zoster virus, either naturally or through vaccination, you are at risk for contracting chickenpox. Your risk increases greatly if you are in close contact with someone who has chickenpox. Chickenpox spreads rapidly through households and school classrooms.

If you have already had chickenpox, this means you have been exposed to varicella and are likely immune to it; you are very unlikely to contract chickenpox again.

Since 1995, a varicella vaccine has been available that exposes a person to varicella without causing chickenpox. The vaccine is 80-90% effective at preventing chickenpox upon future exposure to varicella and even in the cases where a vaccinated person does get chickenpox, it is almost always a very mild case.