Children who aren’t vaccinated against chickenpox are nine times more likely to get the disease, according to the first study that gauges the risk of refusing the 15-year-old immunization.
The vaccine against chickenpox — also called varicella — is the most commonly refused immunization, most likely because many parents suffered through the red-spotted rash and fever when they were young and don’t remember it as that horrible.
But before the 1995 vaccine, chickenpox caused about 10,000 hospitalizations and 100 deaths per year in the United States, researchers said. Immunization has cut those numbers by 80 percent.
The study led by Kaiser Permanente Colorado physicians found that about one in 10 unvaccinated children got chickenpox, compared with one in 100 vaccinated children. The small percentage of vaccinated children who develop the illness usually has a much milder form, researchers said.
Specific data are a help
The fact that children who aren’t vaccinated are at higher risk of chickenpox isn’t surprising, but the researchers expect pediatricians — now armed with specific data — will use the study results to talk to parents about immunizations.
Recent trends indicate public trust of vaccines is eroding, especially among white, well-educated families, said Jason Glanz with Kaiser’s Institute for Health Research and lead author of the study. Some parents are choosing to disregard American Academy of Pediatrics recommendations on vaccines, skipping immunizations entirely or at least delaying them.
“It’s a bit of a mystery why a parent would choose not to get a very effective and safe vaccine,” Glanz said of the chickenpox shot. “They don’t think their children are really at risk, and they don’t think the disease is that serious.”
The reason to get vaccinated isn’t just personal health but also the protection of the community, including children who have compromised immune systems because of diseases such as HIV or leukemia.
Still, vaccine “watch-dog” groups, including the National Vaccine Information Center, argue for more studies that identify who is at risk for having adverse reactions to vaccines.
Dr. Robert Brayden, a pediatrician at Children’s Hospital and a professor at the University of Colorado Denver School of Medicine, is among those likely to cite the study.
“Heretofore, we probably didn’t have a relative risk,” he said. “We said, ‘Your child is a lot less likely to get chickenpox if they’ve been vaccinated.’ But now we can use a number, and that’s useful.”
Brayden said Americans “just don’t understand how much better our world is without chickenpox.”
The chickenpox vaccine is also available for adults, who tend to have more serious complications with the disease.
Specifics of study
The Kaiser study included 133 Colorado children who had chickenpox between 1998 and 2008. For comparison, each child who had chickenpox was matched to four randomly selected children of the same age and sex who never had chickenpox.
Among the 133 kids who had chickenpox, 5 percent had parents who refused the vaccine. Among the 500 children who never got the illness, 0.6 percent were not vaccinated.
The study released Monday is published in this month’s issue of Archives of Pediatrics & Adolescent Medicine.
A 2009 Kaiser study found that children whose parents refuse to have them immunized against whooping cough are 23 times more likely to get that illness.
Jennifer Brown: 303-954-1593 or jenbrown@denverpost.com
