Average incidence of chicken pox is nine- to 10-fold lower for vaccinated children
MONDAY, April 1 (HealthDay News) -- Varicella vaccination is effective for preventing varicella, with effectiveness lasting over a 14-year period, according to a study published online April 1 in Pediatrics.
Roger Baxter, M.D., of the Kaiser Permanente Vaccine Study Center in Oakland, Calif., and colleagues followed a cohort of 7,585 children vaccinated with varicella vaccine in their second year of life (1995) through 2009 for breakthrough varicella and herpes zoster. Of the children, 2,826 received a second dose in 2006 to 2009.
The researchers found that the average incidence of varicella was 15.9 per 1,000 person-years among the vaccinated children, which was nine- to 10-fold lower than in the pre-vaccine era. At the end of the study period, vaccine effectiveness was 90 percent, with no evidence of waning over time. The majority of cases of varicella occurred soon after vaccination, and most cases were mild. None of the children who received a second dose developed varicella. The rate of herpes zoster was lower for vaccinated children than unvaccinated children in the pre-vaccine era (relative risk, 0.61), and cases of herpes zoster were mild.
"This study confirmed that varicella vaccine is effective at preventing chicken pox, with no waning noted over a 14-year period," the authors write.
Several authors disclosed financial ties to the pharmaceutical industry.
Abstract
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