Misconceptions about Immunization
There is no good reason to immunize against
chickenpox (varicella) because it is a harmless disease
Each year in the United States almost 4 million persons suffer from varicella, more than 10 thousand are hospitalized, and approximately 100 die. While the risks of complications from varicella are highest in adolescents and young adults, the burden of disease is greatest among children who suffer 90% of the cases, two-thirds of the hospitalizations, and almost half of the deaths that occur each year in the United States. On average, one child dies each week from this disease and most of those children are healthy at the time they contract varicella. Additionally, children are the group that serve as the primary source of transmission of varicella to groups at higher risk for severe disease, including adults and persons who are not eligible for vaccination. Complications from varicella include soft tissue infections, necrotizing fasciitis, pneumonia, cerebellar ataxia, and encephalitis. The licensure of varicella vaccine in 1995 offered the opportunity to prevent this substantial health burden.
Varicella vaccine is 70% to 90% effective against typical varicella disease and more than 95% effective against severe disease. Most persons who develop varicella who have previously been vaccinated tend to have very mild illness with fewer than 50 skin lesions compared to 200-500 skin lesions in a typical unvaccinated case. Despite the proven efficacy of varicella vaccine, vaccination rates have been low. In 1997, only 26% of 19-through-35-month-old children (median age 27 months) had received a dose of varicella vaccine. This compares with rates of over 90% for most of the vaccines routinely recommended for children. What are the reasons that rates are low?
- First, persons have been concerned about the duration of immunity. Available evidence indicates immunity to varicella should be long term, probably life long. There is no evidence of increasing rates of breakthrough infections over time and no evidence of breakthrough infections becoming more severe with increasing time since vaccination. The great majority of persons who develop illness with a past history of vaccination tend to have very mild disease. Ongoing studies are monitoring vaccine-induced immunity as disease incidence declines to determine the need for an additional dose in the future.
- Second, concerns have been raised that varicella vaccine might cause herpes zoster (shingles) in the future. Current data show the rate of zoster after vaccination is lower than expected after natural infection. While vaccine virus has been cultured from persons with shingles, wild virus appears to be much more likely to cause shingles. Thus, vaccine will probably reduce the incidence of shingles.
- Third, there has been concern that vaccine virus may be transmitted to other individuals who might come down with serious varicella illness. Transmission of vaccine virus from healthy vaccinees has been documented only very rarely, and only when a rash occurs post-vaccination (one published case in 11 million doses distributed). Three to five percent of persons develop rashes, although these data are from nonplacebo controlled trials. The risk of transmission is more than outweighed by the great benefits provided by vaccine. The best way to protect persons at high risk for severe disease (especially those not eligible for vaccine) is to vaccinate their close contacts.
- Fourth, questions have been raised regarding whether the disease is serious enough to warrant prevention. As detailed above, the health burden of varicella is significant. In addition, there are substantial costs related to caring for children with varicella, both in terms of direct medical care costs as well as indirect costs associated with missing work. A cost-benefit analysis of varicella vaccine has indicated that the vaccine saves society more than five dollars for every dollar spent on a varicella vaccination program.
What are the risks of not vaccinating? Taking this risk allows a child to grow up in a partially vaccinated population with less chance of exposure to varicella during childhood. As an adult, the risks of complications from varicella in an unvaccinated person are much greater than the risks in childhood. A uniformly high vaccination rate will assure both adults and children are protected from varicella and its complications. Varicella vaccine is strongly recommended by the Advisory Committee on Immunization Practices, the American Academy of Pediatrics, and the American Academy of Family Physicians. The Centers for Disease Control and Prevention (CDC) urges you to provide varicella vaccine to your susceptible children, adolescents, and adults to reduce the needless health burden of chickenpox.
The text of this article was written by Walter A. Orenstein, M.D., Assistant Surgeon General, Director, National Immunization Program, Centers for Disease Control and Prevention, and was published in the Fall/Winter 1998-1999 edition of Needle Tips, the newsletter of the Immunization Action Coalition.
This page was posted on April 20, 2002.