There was a time when almost everyone got chickenpox as a child—it’s estimated that there were approximately 4 million cases in the United States every year, and 100 to 150 deaths from the disease. All of that changed when a live attenuated varicella vaccine was licensed in 1995 and became one of the recommended childhood vaccinations the following year. And it now appears that the chickenpox vaccine is a star in terms of the number of children who are immunized and in the degree to which it seems to have reduced racial and ethnic disparities in coverage.

Why all of that has happened is not entirely clear, say researchers who analyzed data from the National Immunization Survey (NIS), which tracks annual vaccination coverage for children 19 to 35 months of age. They noted, however, that varicella vaccine is now available free to eligible children through the federal Vaccines for Children program and the State Children’s Health Insurance Program (SCHIP).

What is most surprising, they said, is that the data show white children are often less fully fully immunized against chickenpox than their black and Hispanic peers, a trend that is the opposite of experience with most other childhood vaccinations. They note that this makes varicella vaccination "a success story in eliminating racial and ethnic disparities."

Things look so good, in fact, the researchers said, that it’s likely a Healthy People 2010 goal of 90 percent coverage for varicella vaccine will be met ahead of schedule.

There are cautions, however. Cohorts of children born before the vaccine became available, and who never caught chickenpox when they were small, are now adolescents and at risk of serious illness unless they, too, are immunized. That means it is increasingly important to monitor vaccine coverage and disease history among older children and adults, for whom chickenpox can be a critical illness. For children up to 18 years of age, the 2006 recommended childhood immunization schedule calls for two doses of varicella vaccine, administered at least four weeks apart.

It is not clear how long immunity to chickenpox will last, following infant vaccination. If the effects should wear off in adolescence and adulthood, as many experts believe may happen, people who were immunized before they were three years old may be susceptible to the illness later in their lives.

Another unknown feature of varicella vaccination is whether the immunity it confers will protect older persons from the condition known as shingles, in which dormant chickenpox residing in nerve tissues is triggered by some environmental or immune event, causing a painful and sometimes very serious rash, usually in the waistline but sometimes in the face and eyes. Whether the live attenuated virus in the vaccine given to children will remain in the body for years, possibly triggering later shingles, is not yet known.

The researchers noted that, unlike for other vaccines, living in a non-metropolitan area seemed to increase the possibility that children will not receive varicella vaccination. This "strong and persistent risk factor" may be due, they speculated, to the fact that varicella vaccine must be kept frozen at less than minus 13 degrees Centigrade, and deep freezers may not be readily available in rural areas or their cost may be prohibitive for small practices. They also noted that pediatricians, who are more likely than general practitioners to offer varicella vaccine to their patients, are under-represented in rural areas.

The article, "Uptake of Varicella Vaccination Among Young Children in the United States: A Success Story in Eliminating Racial and Ethnic Disparities," appears in the April issue of the journal Pediatrics.

See also: CHHCS News Alert, August 17, 2005 -- Chickenpox Is Down and So Are Health Costs at http://www.healthinschools.org/2005/aug17b_alert.asp.