If a child had 1 varicella vaccination and developed a vesicular (chickenpox-like) rash at the vaccination site 7 to 10 days after vaccination, does the patient still need the second dose? What if the rash covered the entire body?

If you believe the child had varicella disease (that is, breakthrough varicella) after the first dose, the child does not need another dose. If you are uncertain whether the child had varicella or a rash related to varicella vaccination, the second dose should be administered on schedule. If in doubt, give the second dose. If this was a case of breakthrough varicella, a second dose will not be harmful.