Chickenpox is a mild disease of childhood; complications of the disease are extremely rare in healthy children Adults almost always have more severe infection than children, and disease complications are more common Long-term efficacy of the vaccine is unknown Widespread vaccine usage may shift the age distribution of chickenpox from children to adults Adverse and long-term effects of the vaccine are unknown They could be more serious than measles and mumps vaccines, because the chickenpox virus is associated with cancer and herpes zoster The only justification for the use of the chickenpox vaccine in healthy children has been the saving of parents' time lost from work