Varicella Reporting and Surveillance
Varicella surveillance data are needed to
- Document and monitor the impact of the varicella vaccination program on varicella morbidity and mortality,
- Describe clinical and epidemiological characteristics of varicella cases during the varicella vaccination program,
- Evaluate the effectiveness of prevention strategies, and
- Evaluate vaccine effectiveness under conditions of routine use.
In 2002, the Council of State and Territorial Epidemiologists (CSTE) recommended that states establish case-based surveillance for varicella by 2005. All states were encouraged to conduct ongoing varicella surveillance to monitor vaccine impact on morbidity. States are encouraged to report varicella cases to the National Notifiable Diseases Surveillance System (NNDSS) via the National Electronic Disease Surveillance System (NEDSS).
As of 2020, 39 states have been conducting case-based varicella surveillance. For state-specific reporting requirements, contact the state health department. Information can also be found on CSTE’s website on state reportable conditions.
The following varicella case definitions were approved by CSTE in June 1999. These case definitions for varicella cases and deaths can also be found on CDC’s website on Nationally Notifiable Diseases Surveillance System.
Varicella Clinical Case Definition
An illness with acute onset of diffuse (generalized) maculopapulovesicular rash without other apparent cause. In vaccinated people who develop varicella more than 42 days after vaccination (breakthrough disease), the disease is usually mild with fewer than 50 skin lesions and shorter duration of illness. The rash may also be atypical in appearance (maculopapular with few or no vesicles).
Varicella Case Classification
Probable: A case that meets the clinical case definition but is not laboratory confirmed nor epidemiologically linked to another probable or confirmed case.
Confirmed: A case that meets the clinical case definition and is laboratory confirmed or is epidemiologically linked to a confirmed or a probable case.
Note: Two probable cases that are epidemiologically linked are considered confirmed, even in the absence of laboratory confirmation.
In 1998, CSTE recommended that varicella-related deaths be placed under national surveillance. As of January 1, 1999, varicella-related deaths became nationally notifiable to CDC.
Varicella deaths can be identified through death certificates, which may be available through state vital records systems. In states using electronic records, certificates may be more readily available soon after a person dies. State health departments may also request that local health departments, healthcare providers, and hospitals report varicella deaths that occur in their community.
Since varicella is vaccine preventable, all deaths due to varicella should be investigated. Investigations may provide insight into risk factors for varicella mortality and may help identify missed opportunities for and barriers to vaccination. (For guidance on varicella death investigations, see the Varicella Death Investigation Worksheet [4 pages].
Deaths should be reported to the Division of Viral Diseases at CDC (firstname.lastname@example.org) and to NNDSS via NEDSS.
Resources for Varicella Surveillance
- Chapter on Varicella Manual for the Surveillance of Vaccine-Preventable Diseases
- Varicella Case Definition, from the 2010 CSTE Position Statement
- National Notifiable Diseases Surveillance System (NNDSS)
- Chickenpox Outbreaks
- Varicella Surveillance Worksheet [3 pages]
- Varicella Death Investigation Worksheet [4 pages]
- Reporting Line List for Varicella Outbreak Surveillance [3 sheets] worksheet
- CDC. Evolution of varicella surveillance — selected states, 2000-2010. MMWR 2012; 61(32):609-12.
- Lopez AS, Zhang J, Marin M. Epidemiology of Varicella during the 2-Dose Varicella Vaccination Program – United States, 2005-2014. MMWR Morb Mortal Wkly Rep. 2016 Sep 2;65(34):902-5.