720. Changing Varicella Epidemiology Since Implementation of Routine 2-Dose Varicella Vaccination for Children, Active Surveillance Areas, United States, 2006-2010
Session: Poster Abstract Session: Vaccine Studies, Adjuvants, and Discovery
Friday, October 21, 2011
Room: Poster Hall B1
Background:  In 2006, as varicella outbreaks continued to occur in schools with high 1-dose varicella vaccination (VV) coverage, the Advisory Committee on Immunization Practices recommended implementation of a routine 2-dose VV program for children.

Methods:  We examined varicella incidence, age and VV status of case-patients, and number of outbreaks from 2006 through 2010 in 2 varicella active surveillance areas (Antelope Valley (AV), CA and West Philadelphia (WP), PA). Varicella cases were verified to have had illness with acute onset of diffuse maculopapulovesicular rash without another known cause. On a biweekly basis, community-based sites submitted varicella case reports or documentation of no cases. VV coverage was estimated for WP using immunization registry data for children with ≥1 vaccination recorded and for AV using electronic medical records of children enrolled in a managed care organization.

Results:  Two-dose VV coverage among 5 year olds in 2010 was 96% in AV and 63% in WP.  In 2010, varicella incidence was 0.3/1000 in AV and 0.1/1000 in WP, a 78% decline since 2006 and a 98% decline since vaccine introduction in 1995 in both sites. Incidence declined in all age groups with 79-96% reductions among those aged 5-14 years during 2006-2010. There was no significant change in the proportion of case-patients who were vaccinated with 1 or more doses of VV (66%); in 2010, 30% of vaccinated case-patients had received 2 doses. During 2006-2010, the median age of case-patients with no or unknown doses of varicella vaccine increased from 12 to 15 years in AV and from 15 to 18 years in WP. The median age of vaccinated case-patients fluctuated between 8-9 years in AV and 5-8 years in WP during 2006-2010. In AV, 23 varicella outbreaks were reported during 2006-2010, compared to 46 during 2002-2005. In WP, only 3 outbreaks were reported in WP during both 2002-2005 and 2006-2010.

Conclusion: Varicella incidence has declined in the 3 years since adoption of a routine 2-dose VV program. Differences across sites may be due to VV school entry requirements and varicella control policies. Efforts to promote catch-up vaccination among older susceptible individuals should continue.


Subject Category: I. Adult and Pediatric Vaccines

Stephanie R. Bialek, MD, MPH1, John Zhang, PhD2, Christina Jackson, MPH3, Kendra Viner, PhD, MPH4, Barbara M. Watson, MB, ChB, FRCP(UK), FAAP5, Hung Fu Tseng, Ph.D., MPH6, Adriana S Lopez, MHS2, Rachel Civen, MD, MPH7 and Dana Perella, MSPH8, (1)Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, GA, (2)Centers for Disease Control and Prevention, Atlanta, GA, (3)Los Angeles County Public Health Department (LAC DPH), Los Angeles, CO, (4)Philadelphia Department of Public Health, Division of Disease Control, Philadelphia, PA, (5)Philadelphia Department Public Health, Philadelphia, PA, (6)Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, (7)Los Angeles County Public Health Department (LAC DPH), Los Angeles, CA, (8)Philadelphia Department of Public Health, Philadelphia, PA

Disclosures:

S. R. Bialek, None

J. Zhang, None

C. Jackson, None

K. Viner, None

B. M. Watson, None

H. F. Tseng, None

A. S. Lopez, None

R. Civen, None

D. Perella, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.