To the Editor.
—A vaccine to prevent chickenpox will soon be approved by the Food and Drug Administration for use in the United States. It may be safe and effective for selective use among high-risk children and susceptible adults, especially the immunologically impaired. However, before the vaccine becomes part of the routine childhood immunization package, there must be solid information on the duration and quality of immunity conferred, the effect of the vaccine with respect to later development of herpes zoster, the result of vaccine introduction on the natural transmission of chickenpox, and the availability of the vaccine to all children for whom it is recommended.General use of varicella vaccine by the private sector would probably interfere sufficiently with the natural transmission of chickenpox to cause more teenage and adult cases among the unimmunized who depend on the public sector. That was the experience with mumps vaccine.1,2 Public