Back to Annual Meeting Page		American Public Health Association 133rd Annual Meeting & Exposition December 10-14, 2005 Philadelphia, PA

Abstract #121252

Anand A. Date, Dr¹, Tom Safranek, Dr¹, Dalya Guris, Dr², Adriana Lopez², Mona Marin, MD³, and Anne O'Keefe, Dr¹. (1) Epidemiology, Nebraska Health and Human Services, 301, Centennial Mall, P O Box 95007, Lincoln, NE 68509, 402-471-8820, bvz7@cdc.gov, (2) National Immunization Program, CDC, Viral Vaccine Preventable Disease Branch, Clifton Road, Atlanta, GA 30333, (3) National Immunization Program, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30333

Background: In August 2004, Nebraska mandated varicella vaccination as a school requirement for enrollment in kindergarten and seventh grade. On November 19, 2004, a varicella outbreak was reported in an elementary school with cases among vaccinated students. We investigated the outbreak to determine vaccination coverage, vaccine effectiveness (VE), and risk factors for vaccine failure.

Methods: We collected data on students' vaccination and disease history by using standard questionnaire. We confirmed vaccination status by reviewing school immunization records. A case-patient was defined as any student with an acute generalized maculopapulovesicular rash occurring during August 26 - December 23, 2004. We interviewed case-patients' parents to ascertain disease characteristics. We excluded students with prior varicella from analysis.

Results: Survey response rate was 93% (264/283). Previous varicella history was reported among 46% (122/264) respondents. Varicella vaccine coverage was 80.9% (115/142). Attack rates among unvaccinated and vaccinated students were 66.7% (18/27) and 13% (15/115), respectively. VE was 80.5% (95% confidence interval [CI]: 66%¨C89%). Vaccinated case-patients were more likely to have mild disease (67% versus 11%; p<0.001) and less likely to miss school (mean: 3 versus 5.2 days; p<0.01) than unvaccinated case-patients. Vaccination at age °Ü15 months was associated with an increased risk of vaccine failure (relative risk: 3.8; 95% CI: 1.4¨C10.2).

Conclusion: Varicella VE was consistent with pre-licensure estimates. Achieving higher vaccination coverage through broader school entry requirements might prevent future varicella outbreaks. Consideration should be given to the use of a second dose of varicella vaccine in future.

Learning Objectives:

• Describe the extent of an outbreak
• Discuss the epidemiologic methods used to investigate the outbreak
• Describe method to calculate vaccine effectiveness

Keywords: Outbreaks, Public Health

Presenting author's disclosure statement:

I wish to disclose that I have NO financial interests or other relationship with the manufactures of commercial products, suppliers of commercial services or commercial supporters.