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 study led by Kaiser Permanente Colorado physicians found that about one in 10 unvaccinated children got chickenpox, compared with one in 100 vaccinated children. And the small percentage of vaccinated children who develop the illness usually has a much milder form, researchers said.
The vaccine against chickenpox is the most commonly refused immunization, perhaps because many adults suffered through a bout as youngsters themselves. But before the 1995 vaccine, chickenpox caused about 10,000 hospitalizations and 100 deaths per year in the United States. Immunization has cut those numbers by 80 percent.
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. The chickenpox vaccine is also available for adults, who tend to have more serious complications with the disease.
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.