Stephanie R. Bialek, MD, MPH, from the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues examined varicella incidence rates and disease characteristics in two varicella active surveillance areas – Antelope Valley (AV), CA, and West Philadelphia – from 1995–2010 to assess the impact of the two-dose vaccination program.
The researchers found that the varicella incidence was 0.3 cases per 1,000 population in AV and 0.1 cases per 1,000 population in West Philadelphia in 2010, a decline of 76% and 67%, respectively, since 2006 and a 98% decline at both sites since 1995. Incidence declined for all age groups from 2006–2010, during which time 61.7% of case patients in both surveillance areas had been vaccinated with one dose of varicella vaccine and 7.5% had been vaccinated with two doses. From 2006–2010, varicella-related hospitalizations declined compared with 2002–2005 (>40%) and 1995–1998 (>85%). The number of outbreaks in AV also declined: 12 during 2007–2010 compared with 47 during 2003–2006 and 236 during 1995–1998 (P<0.01).
“Varicella incidence, hospitalizations, and outbreaks in two active surveillance areas declined substantially during the first five years of the two-dose varicella vaccination program,” the authors write.