Assessment of the Status of Varicella Surveillance Practices in the United States, 2012

BACKGROUND:  When the varicella vaccine was recommended for use in the United States in 1996, national varicella surveillance was not adequate to monitor impact of the vaccination program. Varicella was added to the national notifiable diseases list in 2003. An evaluation of varicella data reported to the National Notifiable Diseases Surveillance System (NNDSS) at the Centers for Disease Control and Prevention (CDC), conducted in 2011, demonstrated that national varicella surveillance data were adequate to monitor trends in varicella incidence, however only limited data on varicella vaccination and disease severity of cases are reported to NNDSS.

METHODS:  In collaboration with the Council of State and Territorial Epidemiologists (CSTE), CDC designed an assessment to evaluate current varicella surveillance practices. CSTE piloted the web-based assessment in five states, and subsequently distributed the assessment to state epidemiologists via email. Responses were collected and analyzed by the CSTE National Office. Aggregate responses are presented.

RESULTS:  Response rate for this assessment was 100%, with 51 jurisdictions responding (all 50 states and Washington D.C). A total of 44 jurisdictions (86%) responded that varicella is reportable in their jurisdiction. Among those 44 jurisdictions, the types of varicella reports received include one or more of the following: individual cases (37), outbreaks (33), outbreak-associated cases (28), varicella hospitalizations (23), deaths (28), aggregate varicella case counts (12). The type of varicella surveillance conducted includes any of the following: state-wide case-based (37), regional sentinel case-based (3), outbreak (20), aggregate (3). Of 40 jurisdictions conducting state-wide or sentinel site case-based surveillance, 37 (92.5%) collect information on age, sex, race/ethnicity; 36 (90%) also collect rash onset date, laboratory testing performed, vaccination status; 32 (80%) also collect number of lesions and hospitalizations. At least 50% of jurisdictions also collect clinical (e.g., fever, complications, lesion characteristics, immunocompromised status, treatment) and epidemiologic data (e.g., transmission setting, associated with outbreak). Only 19 (43%) jurisdictions send varicella-specific data to CDC via HL7 messaging. Major barriers stated for not transitioning to messaging include internal competing priorities and funding. 

CONCLUSIONS:  Varicella surveillance practices have improved since varicella was added to the national notifiable diseases list in 2003. A majority of jurisdictions (86%) have made varicella reportable; 91% of those are conducting case-based surveillance. Although most jurisdictions collect information on varicella severity and vaccination status, fewer than half are able to transmit these data to CDC. Strategies are needed to facilitate transmission of varicella-specific data from all jurisdictions to allow for evaluation of impact of the varicella vaccination program.