Precautions with varicella vaccine include Moderate or severe acute illness with or without fever (vaccination is postponed until illness resolves) Recent (within 11 months) treatment with blood products that contain antibody (specific interval depends on the product) Use of specific antiviral drugs: acyclovir, famciclovir, or valacyclovir (if possible, these drugs are stopped 24 hours before vaccination and are not resumed for 14 days after vaccination) Breastfeeding is not a contraindication to vaccination.