Pediatrics

ObjectivesWe examined overall and incremental effectiveness of 2-dose varicella vaccination in preventing community transmission of varicella among children aged 4\ue2\u20ac\u201c18 years in two active surveillance sites. One-dose varicella vaccine effectiveness (VE) was examined in those aged 1\ue2\u20ac\u201c18 years.MethodsFrom May 2009 through June 2011, varicella cases identified during active surveillance in Antelope Valley, CA and Philadelphia, PA were enrolled into a matched case-control study. Matched controls \uc2\ub12 years of the incident case's age were selected from immunization registries. A standardized questionnaire was administered to participants' parents, and varicella vaccination history was obtained from healthcare provider, immunization registry, or parent records. We used conditional logistic regression to estimate varicella VE against clinically-diagnosed and laboratory-confirmed varicella.ResultsOne hundred twenty-five clinically-diagnosed varicella cases and 408 matched controls were enrolled. Twenty-nine cases were laboratory-confirmed. One-dose VE (1-dose vs. unvaccinated) was 75.6% [95% confidence interval (CI): 38.7\ue2\u20ac\u201c90.3%] in preventing any clinically-diagnosed varicella and 78.1% (95% CI: 12.7\ue2\u20ac\u201c94.5%) against moderate/severe, clinically-diagnosed disease (\ue2\u2030\ua550 lesions). Among subjects aged \ue2\u2030\ua54 years, 2-dose VE (2-dose vs. unvaccinated) was 93.6% (95% CI: 75.6\ue2\u20ac\u201c98.3%) against any varicella and 97.9% (95% CI: 83.0\ue2\u20ac\u201c99.7%) against moderate/severe varicella. Incremental effectiveness (2-dose vs. 1-dose) was 87.5% against clinically-diagnosed varicella and 97.3% against laboratory-confirmed varicella. Compared with 1-dose breakthrough cases, 2-dose cases had shorter duration of rash (P=0.01) and were 80% less likely to develop vesicular rashes (P=0.01).ConclusionsTwo-dose varicella vaccination offered improved protection against varicella from community transmission among school-aged children compared with 1-dose vaccination.CC999999/Intramural CDC HHS/United States2016-06-01T00:00:00Z26977081PMC488729