TUESDAY, April 2 (HealthDay News) -- The chickenpox vaccine is very effective at preventing the disease, and its protection doesn't wane over time, new research finds.
"This is a really good vaccine," said the study's lead author, Dr. Roger Baxter, co-director of the Vaccine Study Center at Kaiser Permanente in Oakland, Calif. One dose is enough to protect against most cases and severe infection, he said, while "the second dose just wipes it out."
The study results were released online April 1 in advance of publication in the May print issue of Pediatrics.
Chickenpox, an infection caused by the varicella virus, was commonplace in childhood until the introduction of the vaccine in the United States in 1995. Prior to the vaccine's introduction, more than 90 percent of children contracted chickenpox by the time they were 20 years old, according to the study. Although usually mild, the disease, which causes itchy blisters all over the body, was responsible for about 100 deaths a year.
When the vaccine was introduced, it wasn't clear if one dose would be sufficient, or if protection would wear off over time. Consistent protection was important because chickenpox infection in older teens and adults can be much more serious than it generally is in childhood, Baxter said.
Initial studies suggested the vaccine was between 80 percent and 90 percent effective, but sporadic outbreaks of chickenpox still occurred. In 2006, the Advisory Committee on Immunization Practices recommended that a second dose of varicella vaccine be given when children are between 4 and 6 years old.
The current study included 7,585 children vaccinated with varicella vaccine in 1995 when they were 2 years old. The researchers followed the children's health for 14 years, looking for cases of chickenpox or herpes zoster, which is more commonly known as shingles. Shingles is another type
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