Various formulations of the live attenuated vaccine, based on the so-called Oka strain of VZV, are in use. From both a logistic and an epidemiological point of view, the optimal age for varicella vaccination is 12–24 months. In some countries, one dose of the vaccine is considered sufficient, regardless of age. In the United States, two doses, 4–8 weeks apart, are recommended for adolescents and adults. In a few cases (<5%), vaccinees experience a mild varicella-like disease with rash within 4 weeks. Contraindications to varicella vaccine are pregnancy (because of a theoretical risk to the fetus; pregnancy should be avoided for 4 weeks following vaccination), ongoing severe illness, a history of anaphylactic reactions to any component of the vaccine, and immunosuppression.
A vaccine against herpes zoster (shingles) that was licensed in the United States in 2006 for people aged ≥60 years is very similar to the live attenuated pediatric varicella vaccine, but contains approximately 14 times more virus. The shingles vaccine can significantly reduce the burden of herpes zoster among the elderly, but will not be further discussed in the context of travel vaccines.