Published: May 3, 2007
Updated: May 3, 2007
By Dennis Clements, MD, PhD
Purposely exposing a child to a virulent virus seems like the last thing a parent would want to do, doesn't it? Throughout my pediatric practice, however, mothers have frequently asked me if they could take their children to a neighbor's house to expose them to a youngster with chicken pox. Why? Because chicken pox (which is caused by the varicella virus) has been considered such an unavoidable rite of passage for children that their folks often just wanted to "get it over with." Little did these well-meaning moms realize that chicken pox, while frequently benign, can also cause death and significant disfigurement.
The varicella vaccine turned 10 this past spring. It was licensed in March 1995 after 20 years of study (including several trials conducted at Duke). Before then, at least 90 percent of the U.S. population had evidence of having had varicella infection by 20 years of age. Today, thanks to the development of the vaccine, chicken pox is no longer an inevitable part of childhood. To keep your child as healthy as possible, it's worth learning the facts about chicken pox and how your child can benefit from the varicella vaccine.
While most cases of chicken pox are self-limited with few complications, some individuals are susceptible to more severe effects. In fact, infants under one year of age and adults have a complication rate from chicken pox of five to 10 times greater than that of children between the ages of 1 to 18. Before the development of the varicella vaccine, most children had chicken pox when they were between 1 and 4 years of age. Those who hadn't caught it during that time usually did so in grammar school.
What both families and caregivers often didn't realize during those years was that chicken pox infection carried the potential for significant side effects such as secondary bacterial infection, pneumonia, encephalitis, kidney disease, and fasciitis (spreading skin infection often requiring skin grafts to repair). The approximately 4 million varicella cases that occurred in the U.S. each year resulted in about 10,000 hospitalizations and 100 deaths (evenly distributed between children and adults).
Childhood varicella infection can also affect us later in life. During an initial episode of chicken pox, some of the virus travels up nerve cells and becomes dormant in the spinal cord. As we grow older and become less able to fight infections, the virus can reactivate and travel down the nerve cells and sprout clusters of blisters on our skin, often around the trunk of the body. These lesions are known as shingles. The condition--which affects between 1 and 5 percent of adults (the frequency increases with age) who had chicken pox as children--can be extremely painful and last for weeks; residual pain and tenderness can linger for months.
For all of these reasons, the development of the varicella vaccine was a significant advance. The suggested timeframe for administering the varicella vaccine is between the ages of 12-15 months--at the same time that the MMR (measles-mumps-rubella) vaccine is given. The varicella vaccine has very few local or system side effects and prevents about 85 percent of varicella-caused disease. About 15 percent of varicella-vaccinated children fail to have an optimal response to vaccination and, if exposed to varicella later in life, can develop a very mild form of varicella. Usually this disease looks like bug bites; often, the child has no fever and doesn't seem sick at all.
A very small percentage of vaccinated children will get a normal-looking case of chicken pox when exposed because they did not respond to the vaccine--just as some children do not respond to their first dose of the MMR vaccine. Within the next five years, I believe that it will become routine to recommend a second dose of varicella vaccine to ensure that those few children who do not respond to the initial vaccination are covered.
Currently, between 80 to 90 percent of children are receiving the varicella vaccine at the recommended ages. As good as this statistic sounds, we need to do better. If we do not immunize virtually all children, there will be a group of children who do not receive the vaccine and who also do not get the disease before they grow to adulthood. If we can catch these non-immunized, non-diseased children before 13 years of age, only one shot is required for immunization. For youngsters over the age 12, we have to give two shots--and it's difficult to get children in this age group to see a doctor on a regular basis.
Another potential benefit of the vaccine is that, up to the present, there are 80 percent fewer cases of shingles in vaccinated children than in non-vaccinated children. If these ratios hold, the varicella vaccine may also eventually decrease the number of cases of shingles in older people, which would be a very welcome occurrence. While a vaccine has been formulated to suppress shingles in older adults who had natural chicken pox, a vaccine that prevents the disease in the first place would be even better.
Chicken pox has been a disease of childhood--and shingles a scourge of older adulthood--for centuries. The introduction of the varicella vaccine offers real potential to improve the health of children and adults alike. To make good on that promise, we need to make sure that all children receive the vaccine.
Dennis Clements, MD, PhD, is the chief of primary care pediatrics at Duke Children's Hospital.