The seroprevalence of chickenpox in countries with temperate climate is very high among young people. Only 4% of the infections occur in adults but the clinical course is usually more severe than in children. In adults, The mortality is approximately 40 times higher and the complication rate 25 times higher than in children. Pneumonia is the most frequent complication in adults and may be extremely severe in immunocompromised patients and in pregnant women. Pneumonia must be promptly treated with intravenous aciclovir. Vaccination is indicated in young seronegative patients with supplemental risk factors for severe complications. It is also effective post exposure, preventing or modifying the illness course in up to 90% of exposed people if given within 3 days. Immunoglobulins may be effective as late as 96 hours after exposure. They are frequently used for exposed people at high risk of severe disease, when varicella vaccine is contraindicated.