Varicella zoster virus the ACIP recommended a second dose of vaccine before school entry to ensure the maintenance of high levels of varicella immunity. In 2006, the United States Food and Drug Administration approved Zostavax for the prevention of shingles. Zostavax is a more concentrated formulation of the Varivax vaccine, designed to elicit an immune response in older adults whose immunity to VZV wanes with advancing age. A systematic review by the Cochrane Library shows that Zostavax reduces the incidence of shingles by almost 50%. Shingrix is a "V. zoster" vaccine developed by GlaxoSmithKline which was approved in the United States by the
Rare disease treated, are excluded from their definition. The definitions used in the medical literature and by national health plans are similarly divided, with definitions ranging from 1/1,000 to 1/200,000. Because of definitions that include reference to treatment availability, a lack of resources, and severity of the disease, the term "orphan disease" is used as a synonym for "rare disease". But in the United States and the European Union, "orphan diseases" have a distinct legal meaning. The United States' Orphan Drug Act includes both rare diseases and any non-rare diseases "for which there is no reasonable expectation that the cost of developing