Varicella vaccine mild and have not been associated with serious complications. Approximately 5% of children who receive the vaccine develop a fever or rash. Adverse reaction reports for the period 1995 to 2005 found no deaths attributed to the vaccine despite approximately 55.7 million doses being delivered. Cases of vaccine-related chickenpox have been reported in patients with a weakened immune system, but no deaths. The literature contains several reports of adverse reactions following varicella vaccination, including vaccine-strain zoster in children and adults. The Varicella zoster vaccine is made from the Oka/Merck strain of live attenuated varicella virus. The virus was initially obtained
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