Posted on Wed, Feb. 06, 2002

Chicken pox close to being wiped out
A vaccine introduced in 1995 helped lower the number of cases. In West Philadelphia, they dropped 79 percent.
By Susan FitzGerald
Inquirer Staff Writer

Chicken pox, once a rite of childhood, is headed for near-extinction, going the way of measles and mumps.

A study of chicken-pox cases in West Philadelphia and two communities in Texas and California found that a vaccine introduced in 1995 reduced cases of chicken pox by about 80 percent in six years, according to a study in today's Journal of the American Medical Association.

Researchers said they believe the viral illness, known for its itchy red spots, is steadily declining throughout the country.

Before the vaccine was introduced in 1995, about 4 million people in the United States, most of them children, got chicken pox each year, resulting in about 11,000 hospitalizations and 100 deaths annually. Late winter and spring are prime chicken-pox season.

Most children weathered the discomfort of the disease - fever and sometimes hundreds of blisters that scabbed over - without much problem, but the disease can have serious complications, including skin infections, pneumonia, and encephalitis, a life-threatening brain inflammation.

Chicken pox is still far from being completely wiped out - there are small outbreaks of the disease at six Philadelphia schools right now - but the study illustrates the far-reaching effect a vaccine can have on the course of childhood illness.

"This is a real success story," said Jane Seward, a vaccine expert who headed the study at the federal Centers for Disease Control and Prevention.

The study found that as more children became vaccinated, the number of chicken-pox cases plummeted, and fewer people were hospitalized with complications of the disease.

In West Philadelphia, the number of chicken-pox cases fell from 1,197 in 1995 to 250 in 2000, a decrease of 79 percent. Hospitalizations for chicken pox went from 20 in 1996 to 6 in 2000, said Barbara Watson, medical consultant to the Philadelphia Department of Public Health's vaccination program, who directed the research here.

In Antelope Valley, part of Los Angeles County, the number of cases declined 71 percent during the time of the study. Travis County, Texas, which includes Austin, saw an 84 percent decrease.

The most marked declines were in children between the ages of 1 and 4, but the disease was down in all age groups of children and adults.

The study's findings were so convincing, Seward said, that they should help put to rest any doubts people still have about the importance of the chicken-pox vaccine.

"The vaccine works, it's safe, and this is the final piece of the puzzle. If you use it, the disease goes away," Seward said.

The chicken-pox vaccine, manufactured under the trade name Varivax by Merck & Co. of West Point, Montgomery County, had a lukewarm reception among some doctors and parents when it first came on the market.

Many people saw chicken pox, or varicella, as more of a nuisance than a serious disease. There also were some concerns about the vaccine's effectiveness and lasting power, prompting worries that people would come down with the disease in adulthood, when it can hit harder.

"Shouldn't we just let natural infections occur?" was the thinking of some critics, said Paul Offit, chief of infectious disease at Children's Hospital of Philadelphia. Some parents said no to the chicken-pox vaccine while getting all the other shots for their children.

But after a slow start, today "it's pretty well accepted by most people," said William Sharrar, chief of pediatrics at Children's Regional Hospital at Cooper Hospital-University Medical Center in Camden.

Because chicken pox is not a disease required to be reported to the CDC, researchers had to set up a study to measure the effect of the new vaccine. Places such as doctors' offices, hospitals, child-care centers, and schools in West Philadelphia and the other two communities reported to health officials all cases of chicken pox they saw.

Overall, cases declined as immunization rates went up, Watson said.

In 1997, 43 percent of Philadelphia children ages 19 months to 35 months had received the chicken-pox vaccine; by 2000, nearly 84 percent in the same age category were vaccinated.

Philadelphia is ahead of the nation when it comes to vaccinating for chicken pox, in part as a result of the increased awareness stemming from the study, Watson said. In 2000, about 68 percent of preschoolers nationwide were immunized.

Twenty-six states require chicken-pox vaccination for entry into a child-care center, and 19 states require it for school admission. In Pennsylvania, it is required for enrollment in licensed child-care centers and will be required for school admission starting this fall, according to state officials. In New Jersey, the vaccine is not needed in either instance. In Philadelphia, the chicken-pox vaccine is now required for school admission.

Pediatric experts recommend the vaccine be given to babies between the ages of 12 months and 18 months.

Even with the vaccine, some children will get chicken pox. Watson said that every year about 2 percent of vaccinated children will come down with the illness, though the disease will usually be very mild.

As more children get the shot, the disease should fade even more.

"If you have a virus going around and you have enough immunized individuals, it can't survive," Watson said.

Susan FitzGerald's e-mail address is sfitzgerald@phillynews.com.