Varicella Disease in One-Dose Versus Two-Dose Varicella Vaccine Recipients, Los Angeles County, Department of Public Health (LAC DPH), Antelope Valley (AV), California

Background: LAC DPH has conducted active surveillance on varicella disease since 1995.  In 2006, the Advisory Committee on Immunization Practices (ACIP) endorsed the second childhood vaccine dose due to persistent varicella disease in children with childhood varicella vaccination.

Objectives: Compare the clinical presentation of varicella disease and laboratory validation of varicella disease diagnosis in single dose varicella vaccinated varicella cases versus varicella cases receiving two vaccine doses. 

Methods: A standardized case report is completed for all verified cases by phone interview with the case’s parent/guardian, or a medical chart review is used to validate the diagnosis of varicella.  Varicella cases had illness with acute onset of diffuse maculopapulovesicular rash without other cause. Breakthrough (BT) varicella occurred >42 days after vaccination.  Vaccination dates for varicella vaccine and/or MMRV were validated through vaccination records provided by case, school or medical provider. 

Results: From 2007 to 2008, 318 BT cases were documented.  Of these, 289 (90.9%) received the first varicella vaccine dose and 29 (9.1%) received two vaccine doses.  245 (84.8%) of single dose BT cases and 21 (72.4%) two-dose BT cases reported macular/papular lesions.  The majority of cases had <50 lesions (213, 73.7%) for single-dose and (21, 72.4%) of two-dose vaccinees.  Healthcare providers diagnosed 240 (83%) in single-dose and 18 (62.1%) for two-dose BT cases.  33 (11.4%) one-dose BT cases had PCR- testing of lesions, 17 (5.9%) were PCR- positive.  Two (6.9%) two-dose cases had PCR- testing, one (3.4%) case was PCR- positive. 

Conclusions: Varicella disease continues to be documented in individuals who received two doses of varicella vaccine. Symptoms of breakthrough varicella were similar in one dose versus two dose BT cases.  More laboratory confirmation is needed to document the varicella disease and effectiveness of one dose versus two doses of varicella vaccination.