HealthDay News — Since the introduction of a two-dose vaccination program varicella incidence has declined drastically at two active-surveillance sites, researchers have found.

From 2006 to 2010, varicella incidence declined 76% and 67%, respectively, in Antelope Valley, Calif. and West Philadelphia, Stephanie R. Bialek, MD, MPH, of the CDC in Atlanta, and colleagues reported in Pediatrics.

In 2010, varicella incidence was 0.3 per 1,000 population in California and 0.1 cases per 1,000 population in West Philadelphia — representing a 98% decline at both sites since 1995, the researchers reported.

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Incidence declined for all age groups from 2006 to 2010, during which time 61.7% of case patients in both surveillance areas had been vaccinated with at least one dose of varicella vaccine and 7.5% had been vaccinated with two doses.

During this time-period, varicella-related hospitalizations declined more than 40% compared with hospitalization rates from 2002 to 2005 and more than 85% compared with 1995 to 1998. 

The number of outbreaks in Antelope Valley also declined, falling to just 12 from 2007 to 2010 compared with 47 during 2003 to 2006, and 236 during 1995 to 1998 (P<0.01).

“Declines in incidence across all ages, including infants who are not eligible for varicella vaccination, and adults, in whom vaccination levels are low, provide evidence of the benefit of high levels of immunity in the population,” the researchers wrote.


  1. Bialek SR et al. Pediatrics. 2013; doi:10.1542/peds.2013-0863.