A study in the Journal of the Pediatric Infectious Diseases Society reports that since a varicella virus vaccine first became available in the United States, a significant reduction has been seen in varicella cases and a greater protection has been offered to those who are not immunized against the virus.

Jessica Leung, MPH, and Rafael Harpaz, MD, MPH, both from the Centers for Disease Control and Prevention (CDC), observed a 93% reduction in hospitalizations linked to varicella infection in 2012 compared with 1994 (one year prior to the introduction of the vaccine in the U.S.). 

After a second dose was recommended in 2006, hospitalizations declined by 38% and outpatient visits related to the illness dropped by 84% compared to before the vaccine

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The largest declines were among children and adolescents aged 1–19 years old, but substantial reductions were also seen in infants <12 months and in adults, who are often not immunized. This suggests possible herd immunity with vaccination.

Researchers added that testing increased during office visits for varicella infection, from 6% in 2003 to 17% in 2012. Lab testing will become increasingly important as cases continue to decrease and clinicians become less familiar with its clinical presentation.


1. CDC. JPIDS. 2015; epub ahead of print. 

This article originally appeared on MPR