Chickenpox Vaccine Is Swaying Skeptics
The country’s first community-wide study of the chickenpox vaccine--conducted in the Antelope Valley--suggests that inoculations led to an 80% reduction in cases over five years and could end the disease’s long run as a painful, itchy and occasionally dangerous rite of childhood.
Between 1995, when the vaccine was introduced, and 1999, chickenpox cases dropped from 2,934 to 587 in the region, according to the ongoing study by Los Angeles County health officials for the U.S. Centers for Disease Control and Prevention. Rates declined in every age group, most dramatically among children 1 through 4 years old. The overall number of disease complications, including secondary bacterial infections, took a dive as well.
Researchers hope their findings will help dispel resistance from physicians and parents who objected to the vaccine from the outset as unnecessary, potentially risky and otherwise ill-advised. If the vaccine is widely used, they say, chickenpox should join the ranks of measles and mumps as an officially preventable childhood infection.
“The bottom line is . . . the vaccine works,” said Dr. Laurene Mascola, one of the researchers and chief of the county’s acute communicable disease control branch. “You can prevent [chickenpox].”
The decline in the Antelope Valley was all the more significant because vaccination was voluntary. About 70% of 1- and 2-year-olds were inoculated. California has one of the highest chickenpox inoculation rates in the nation. Next year for the first time the state will mandate vaccination for children entering its schools or day-care facilities. About half the states in the country have enacted such mandates, although health officials say the ideal time to vaccinate is around 1 year of age.
The Antelope Valley is one of three areas selected by the CDC for study of the vaccine’s impact. The other two are in west Philadelphia and Travis County, Texas.
But the California study, focusing on a relatively isolated region of about 300,000 residents, is the first in the country to assess the impact by tracking every known case of chickenpox. Sources of case reports included private doctors, hospitals, schools, correctional institutions and employers.
Besides demonstrating the vaccine’s efficacy, researchers said, they showed its economic and social value. In 1995, according to the findings, chickenpox victims and their caretakers in the Antelope Valley missed 14,842 days of work and school; that number plummeted 82%, to 2,718, in 1999.
The chickenpox virus, or Varicella zoster, is extremely contagious, spread by touch or airborne droplets. Most children are infected before the age of 10 and are sick for about 10 days with painful, itchy rashes, fevers and fatigue. As many as 4 million infections occur annually in the United States.
Though chickenpox is generally far less virulent than other childhood scourges, it occasionally leads to complications, scarring and even death. Before introduction of the vaccine, it caused as many as 10,000 hospitalizations and killed about 100 children and adults each year.
The Antelope Valley study showed that complications arose in 8% to 13% of cases, most commonly among infants and adults. Adults are far more likely to suffer severely than youngsters, and may encounter complications such as pneumonia and encephalitis. Nationally, between 5% and 10% of adults are believed to be susceptible to chickenpox. Children, as well, may develop complications, including severe invasive streptococcal infections.
“It’s true that it’s [usually] a mild disease, but it also results in mortality, and there’s no telling who will die from it,” said Aisha Jumaan, an epidemiologist with the CDC’s Vaccine Preventable Diseases Branch. “Why take those chances?”
At the time the vaccine was introduced, in March 1995, some parents and physicians hesitated. They contended that Varicella is a benign disease and that children--and doctors--need not be burdened with one more shot. They worried that the level of immunity conferred by the vaccine would not persist or that the vaccine itself would not be safe.
Others argued that, with less circulation of the virus among children, adults’ immunity--which can be boosted by repeated exposure to the wild virus--would decline.
The Antelope Valley study should allay some of those concerns, researchers said. For example, the decline in disease across age groups suggests that when children are inoculated, adults are less likely to get sick as well, Jumaan said. She said that the vaccine produces adverse reactions in less than one case per 100,000 and that the effects are generally mild--rashes, swelling, soreness or fever.
Dr. Brian Greenberg, an Agoura Hills and Tarzana pediatrician who specializes in allergies and immunology, initially was among the hesitant. But “as time went on and I started looking at the data [in his seven-doctor practice], I changed how I was thinking,” he said. “Here we are, five years out, and we’ve definitely seen a reduction in the number of cases.”
He described the Antelope Valley findings as “very impressive.” Yet he and others said they are seeing too many “breakthrough cases”--instances in which children get chickenpox despite receiving the vaccine.
Los Angeles County researchers found that, in 1999 alone, slightly more than 12% of their cases were among people who had been vaccinated.
Because of such cases, some experts predicted the need for booster shots at some point. “I can’t imagine it won’t” be needed, Greenberg said. “Otherwise we are going to have something like we did with measles outbreaks on college campuses.” About 10 years ago, students and others got measles, even though they had been vaccinated.
Mascola agreed that booster shots may eventually be called for. But for now, only one shot is recommended for children 13 or younger, and she is most concerned about children and adolescents who have not received any protection.
She noted that officials in California are considering whether to require inoculation among unvaccinated seventh-graders, in addition to those entering the state’s school system for the first time. After age 13, two doses of vaccine are needed about a month apart.
In general, Mascola said, the vaccine is 85% to 93% effective, and in cases where the disease breaks through the vaccine, the course is generally “very mild.”
Mascola and others emphasized that the best protection comes from vaccination around 1 year of age, since the peak years of infection are 1 through 4.
“If you wait until 2 or 3 years of age, you’re missing the boat,” she said.
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Medical Success
In the five years since the chicken pox vaccine was introduced, the disease declined 80% in a study conducted in the Antelope Valley.
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Source: L.A. County Department of Health Services
