Varicella and Zoster (Shingles)

Abstract

A live attenuated vaccine against varicella (later also used to prevent zoster) was developed in 1974 by Takahashi and colleagues. Varicella vaccine was licensed for universal immunization of healthy children in the United States in 1995. It is also now used for this purpose in at least 15 additional countries all over the world. Varicella is disappearing in the US. Varicella vaccine has proven extremely safe and side effects are unusual, mild, and less serious than varicella or its complications. 85% of children are protected completely after 1 dose; the 15% who develop varicella despite immunization usually (but not always) have mild infections. These 15%, however, can transmit the wild type virus to others. Therefore, for optimal effect, 2 doses are required, mostly to address children who did not have an optimal primary immune response after the first dose. Waning immunity does not seem to pose a serious problem, but surveillance of vaccinees is continuing. It was demonstrated in 2005 that at a high dose of vaccine – 15 times higher than that used for prevention of varicella in children - zoster in adults can also be safely prevented. The live attenuated zoster vaccine is effective in approximately 50% of healthy individuals over age 60 who have had varicella in the past, and therefore have latent infection with varicella-zoster virus. It is given as one dose, but its effect runs out about 8 years after vaccination. In 2017, a new vaccine against zoster was also introduced. This is a subunit vaccine which does not contain contagious virus. It is even more effective than the older zoster vaccine and is over 95% effective in adults 50–≥70 years of age in preventing zoster and post herpetic neuralgia.