The Success of the Chickenpox Vaccine

Before the introduction of the varicella vaccine in 1995, about 4 million Americans a year, more than 90 percent of them under age 15, contracted chickenpox, and about 10,000 were hospitalized because of it. By almost all measures, the vaccine has been a resounding success: From 1995 to 2005, the number of chickenpox-related hospitalizations declined by more than 75 percent. Child deaths from the disease, which had been at about 50 or 60 a year, became extremely rare. And medical costs associated with varicella dropped by 74 percent.

The vaccine has worked so well that some parents no longer view the disease as a health threat. It is. Chickenpox outbreaks tend to start with unvaccinated kids, who put even immunized kids at risk of getting the disease. That's because a single shot of vaccine (recommended at 12 to 15 months of age) fully protects only 80 to 85 percent of children against chickenpox; the others can still get "breakthrough" varicella. In June 2006, the American Academy of Pediatrics (AAP) and the Advisory Committee on Immunization Practices to the U.S. Centers for Disease Control and Prevention recommended a second dose, a booster, of varicella vaccine for kids who are 4 to 6. "If you do have a widespread outbreak, and no vaccine is 100 percent effective, you're still better off if you've had the vaccine," says David Kimberlin, a member of the American Academy of Pediatrics' committee on infectious diseases, who urges all parents to get their kids immunized.

In the September issue of the journal Pediatrics, CDC authors discuss successes and challenges of fighting chickenpox, which most commonly causes rash, itching and fever, but in extreme cases can result in skin infections, scars, pneumonia, brain damage and death. NEWSWEEK's Karen Springen talked with Jane Seward, co-author of the Pediatrics paper and deputy director of a CDC division dedicated to immunizations and respiratory diseases, about the importance and safety of the vaccine. Excerpts:

NEWSWEEK: Why is it so important to get this vaccine?
Jane Seward: The reason it was recommended back in 1995, is that chickenpox, despite a lot of people's perception that it's a mild childhood disease, can result in complications and death. The most common severe complications of chickenpox are pneumonia, encephalitis, bacterial infections and bleeding disorders. You've got all these skin lesions, sites of entry for bacteria. You can get co-infected with flesh-eating bacteria. Before the vaccine, about 100 to 150 people died a year from chickenpox, and about 10,000 or 11,000 were hospitalized for chickenpox. You can't tell who's going to be the unlucky one. I talked to the parent of a 5-year-old child who died from chickenpox.

How many people now die each year from chickenpox?
We talk about the decline in deaths being over 90 percent in children. We used to have 50 or 60 deaths a year in children. Now it's extremely rare. In 2005, there was only one death in people under 20.

What about the holdouts, parents who don't want to vaccinate their kids?
Varicella vaccine has never been implicated in causing autism. There is no mercury in any of the live viral vaccines, including measles, mumps, rubella and this one.  Preservatives were used in killed vaccines, such as DPT (diphtheria, pertussis and tetanus), but they haven't been in seven or eight years. They were all removed in 2001. I'm working a lot on measles as well. We've seen an increase in measles this year, mainly in children whose parents choose not to vaccinate them. I think it's our job as public health officials to provide the best information for parents to be able to make the best choice for their child, including understanding the safety and effectiveness of the vaccine. It's their decision, of course. They can talk with their providers about that.

What are the side effects of the varicella vaccine?
The side effects are the same effects that the wild virus has, because it is a weakened version of the wild virus. Rarely, you can get a mild rash, like chickenpox, or any of the complications of chickenpox. But those occur very, very rarely.

Why does the vaccine fail in some people?
The vaccine does not provide 100 percent protection against disease. The vaccine provides about 85 percent protection against all disease and close to 100 percent protection against severe disease. The one or two out of every 10 who might come down with varicella after the vaccination most commonly get mild illness. Nevertheless, that can still transmit to others and cause some small outbreaks. To try to decrease that is why the second dose was recommended. We're not reporting in this review the effect of the second dose yet. There hasn't been enough time. We would anticipate that it would have a further effect in decreasing the incidence. We'll have to see.

The varicella vaccine is a relative bargain, right?
I think it's $50 or somewhere in that range. Everything has to be weighed out with cost and effectiveness. The vaccine, both the one- and two-dose program, are cost-effective when you consider societal benefits, as well as direct medical benefits—parents staying home from work to take care of sick children.

What about the "catch-up" vaccine?
It's recommended that children who got a first dose get a second dose, at absolutely any age. When they have their next checkup, a pediatrician should be offering the second dose. A lot of states now have requirements for varicella vaccine for one dose, and some of them are now updating their state requirements to require two doses. It will take a few years, but primary-care physicians are increasingly going to be offering that dose for children as they come in for routine checks.

Should we vaccinate very young kids?
A lot of these diseases are very contagious and chickenpox is one of them. There was a very high incidence in elementary schools because kids got together at that age, at 5 or 6. As children started to congregate at preschool ages, chickenpox became more common [with that group] because of mixing and higher contact rates. That was the age group that the vaccine was recommended in first, in children 12 to 18 months.

Why don't we do it at birth?
Because it's a live viral vaccine, and antibodies the mother has from having the disease in her childhood would interfere with the vaccine's immune response. Typically we don't give live viral vaccines until 12 months or older, when maternal antibody has declined.

How many are just saying no to the vaccine?
We'll be getting our new data on that in a week. The national immunization rates are released in September every year. We'll see what the coverage was.

To avoid outbreaks, don't we need a high percentage of kids to get the vaccine?
Most states have requirements for elementary school, so we catch up a number of those 10 percent who don't have it before school. The outbreaks now are much, much smaller than in the past.

What about getting chickenpox during pregnancy?
It can cause infection of the fetus and a constellation of severe birth defects, or congenital malformations cause congenital varicella syndrome. Children [may be] born with mental retardation, small skulls and eye defects.

Parents should understand that although chickenpox is often considered to be not a severe childhood illness, there can be some serious consequences of chickenpox, including deaths and hospitalizations. Using the vaccine for 10 years now has resulted in [a] very sharp decline in the disease and its consequences.

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