Originally developed in Japan in 1974 by M. Takahashi, varicella vaccine
(Oka) was first licensed for routine use in the US in 1995. While initially
somewhat controversial, it has since gained wide acceptance, and varicella
vaccination is now a prerequisite to entry into daycare and/or primary school
in roughly half of the 50 US states. A CDC goal for 2010 is to immunise more
than 90% of susceptible children against varicella.
Prior to vaccine
use, there were over 4 million cases of varicella each year in the US, with
about 100 deaths and 11,000 hospital admissions. CDC data indicate that this
pattern is now changing significantly as a result of vaccine use. Over 20
million doses of varicella vaccine have been distributed in the US, and the
vaccine has proven to be extremely safe, with incidences of zoster and
transmission of the virus to non-vaccinated individuals both being rare.
Serious adverse reactions to the vaccine are also extremely rare. Protection
against varicella is currently in the region of 90%.
Studies in adults and in children show very little indication of any loss of immunity over time following administration of the varicella vaccine. Varicella vaccination is currently being investigated as a potential means of protecting the elderly against zoster by boosting their cell-mediated immunity to varicella zoster virus. Efforts to develop a combined measles, mumps, rubella and varicella (MMRV) vaccine are continuing.