Overview
- A live attenuated vaccine against varicella (later also used to prevent zoster) was developed in 1974 by Takahashi and colleagues.
- The varicella vaccine was licensed for universal immunization of healthy children in the United States in 1995 and is now used for this purpose in at least 15 additional countries worldwide. Varicella is disappearing in the US.
- The vaccine has proven extremely safe, with side effects being unusual, mild, and far less serious than varicella or its complications.
- 85% of children are fully protected after 1 dose; the remaining 15% who develop varicella despite immunization usually have mild infections. These children, however, can still transmit the wild-type virus to others.
- Therefore, for optimal protection, 2 doses are recommended, primarily to cover children who did not mount an adequate primary immune response after the first dose.
- Waning immunity does not appear to be a major issue, although vaccinees continue to be monitored. In 2005, it was demonstrated that a high-dose version of the vaccine—15 times higher than the standard childhood dose—can safely prevent zoster in adults.
- The live attenuated zoster vaccine is effective in approximately 50% of healthy adults over 60 who have had prior varicella infection. It is administered as a single dose, but its protection lasts about 8 years.
- In 2017, a new subunit vaccine for zoster was introduced. This vaccine does not contain live virus and is even more effective than the older zoster vaccine, with over 95% efficacy in adults aged 50–70+ years in preventing both zoster and postherpetic neuralgia.
