Chickenpox (varicella-zoster) is one of the ‘classic’ childhood illnesses, typically mild and survived by almost every child. In the recent past, parents would deliberately expose their children to the disease because following infection lifelong immunity would usually result. Risk of complication from the natural infection is low.
A vaccine for chickenpox was introduced in North America and Europe in 1995. It was offered as a cost effective solution for parents who lost time off work to care for their children. But because the effects of a single vaccine are gone by the age of 10, additional doses were required. Additional routine doses of this vaccine at ages 10-13, however, have had unanticipated ramifications for the entire population.
Since the introduction of the chickenpox vaccine, prevalence of a related strain herpes-zoster (shingles) has increased as much as 63% in US children aged 10-19. Shingles is a viral infection of the nerves by the varicella virus, and causes painful blisters. While the CDC has described this development as aberrant, UK health officials believe there is a connection. The UK Health Protection Agency revealed in 2008 that the pediatric chickenpox vaccination had increased the prevalence of shingles among teens, adults and the elderly. They believe that exposure to the natural form of the disease in children was important. This natural exposure actually boosts the immunity of the population as a whole. The chickenpox vaccine is not part of routine pediatric schedule in the UK. In the USA, however, the vaccine continues to be administered to infants despite evidence that the population as whole is actually harmed by it.
On the other hand, the risk of death from chicken pox (less than 1 in 200,000 for children under age 5 prior to the introduction of the vaccine, as shown in Disease Risk – Varicella) is reduced to almost zero by the vaccine.
The varicella vaccine is offered individually, and has also been combined with the MMR (Measles-Mumps-Rubella) to make an MMRV (Measles-Mumps-Rubella-Varicella) vaccine. There are concerns about adverse interaction when different live viruses are combined in one vaccine. Merck’s ProQuad MMRV vaccine was approved in 2005 but in 2008, because of a twice-as-high risk of fever-related convulsions, the CDC dropped its preferential recommendation for this four-in-one vaccine (see ProQuad). For more information, see SmartVax Approach to the MMR Vaccine.
Given that vaccination may increase the risk of shingles later in life, and the low risk of death or permanent injury from chicken pox, a parent might consider whether the benefits of this vaccine are worth its risks. If a parent chooses for the child to receive varicella vaccine, the parent might consider whether to utilize the single varicella vaccine rather than the combination MMRV vaccine.
 Cliven, R.., et al., “The incidence and clinical characteristics of herpes zoster among children and adolescents after implementation of varicella vaccination,” Pediatri Infect Dis J. 28 (11) (Nov. 2009): 954-9.