Development of a live varicella vaccine--past and future.

Background of the development of a live varicella vaccine, including studies on the attenuation of measles and polioviruses, and transformation experiments of cultured hamster and human cells with conditional lethal mutants of adenovirus and herpes simplex virus were described. Varicella-zoster virus (Oka strain) was passaged in guinea pig cells, and the resulting virus (vaccine virus) was found to have a higher affinity to guinea pig cells. It was recently proved that variations of base sequence occurred exclusively in gene 62 (immediate-early gene) in comparison of vaccine Oka virus and parent Oka virus. This variation is presumed to have occurred during passage in guinea pig cells. Live varicella vaccine (Oka strain) has increasingly been used throughout the world. It was also found in a preliminary study that giving the vaccine to the elderly enhanced humoral and cell-mediated immunity, leading to a prevention of post herpetic neuralgia. A large field trial is now going on in the United States to immunize the elderly for the purpose of prevention of herpes zoster, particularly post herpetic neuralgia.