The chickenpox vaccine, also known as the varicella vaccine, was first made available in 1995, and since its introduction there have been significantly fewer cases in the United States. In 2006, the recommendation for a second dose of the vaccine was added, and both the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) recommend that kids get this second dose between ages 4 and 6.
Related: Is the Chickenpox Vaccine Safe?
Now, a new study confirms that the added dose has continued to decrease the number of outpatient visits and hospitalizations due to chickenpox. The study, published in the Journal of the Pediatric Infectious Diseases Society, examined national health data from 1994 to 2012.
CDC researchers found that between 2006 and 2012, after the two-dose vaccination recommendation was introduced, outpatient visits decreased by 60 percent and hospitalizations declined by 38 percent.
While the most significant declines were among the vaccine's targeted population (1-19 year olds), they also found a reduction in cases among babies younger than 12 months (who haven't yet had the vaccine) and adults (who are often unvaccinated), which suggests the potential of herd immunity.
"We saw significant declines in rates of varicella after the one-dose vaccine was recommended in 1995 in the U.S., and we're continuing to see additional declines in varicella after two doses were recommended in 2006," said Jessica Leung, the study's co-author.
Caitlin St John is an Editorial Assistant for Parents.com who splits her time between New York City and her hometown on Long Island. Follow her on Twitter: @CAITYstjohn
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