The Varivax vaccine is given to prevent Chickenpox, a viral exanthem (viral rash) with fever, seen commonly in childhood in the past. The vaccine is approximately 85% effective in preventing chickenpox after one dose. Two doses of Varivax are given to confer excellent prevention of Chickenpox at 98%, but 100% protection against severe varicella. The second dose is given at 4 years of age.

Since beginning the national Chickenpox vaccination program, the incidence of Chickenpox has fallen dramatically. Side effects of the vaccine are quite rare and include the development of a few small vesicles on the skin (these look like chickenpox lesions) which resolve over a few days. The vaccine does not prevent the occurrence of Shingles (see section on Chickenpox) but does make it less likely to occur. Varivax is a live virus vaccine, so it should not be given to a child who is immanuel-compromised.