Perspective on live varicella vaccine.

The attenuation of varicella-zoster virus (VZV) by Takahashi in 1974 was a remarkable achievement. It swiftly led to development of a live vaccine against chickenpox, which was initially tested in Japan. With its successful employment in immunocompromised children to prevent morbidity and mortality due to varicella, the vaccine began to be tested in healthy children in Japan and elsewhere. In the United States, vaccine use progressed from extensive clinical trials that demonstrated safety and efficacy to universal immunization of healthy infants and children. In the past 10 years, >30 million healthy American individuals, mostly children, have been vaccinated. With increasing use of vaccine, there has been a concomitant decrease in the incidence of disease, along with decreases in hospitalizations and deaths due to VZV. To improve protection, however, a 2-dose schedule of immunization was recommended for routine use in all children by the Centers for Disease Control and Prevention in June 2006. At roughly the same time, licensure of the combined measles-mumps-rubella-varicella vaccine was completed, which allowed harmonization of immunization against these 4 viruses with 1 injection given twice in childhood. Concomitantly, a version of the varicella vaccine with 10 times the titer was developed for immunization of healthy individuals >60 years of age against herpes zoster (HZ). Although elimination of VZV from human populations may not yet be possible, the combined approach of immunization against both varicella in childhood and HZ in adulthood in the developed world are predicted to dramatically increase our control of this troublesome virus.