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Wednesday, March 23, 2005 - 11:25 AM
61

Validity of Reported Varicella History As A Marker for Varicella-Zoster Virus (VZV) Immunity Among Different Age Groups

Donovan Robinson1, Dana Perella1, C. Victor Spain1, Alexander Fiks2, Paul Gargiullo3, Barbara Watson1, Karl Heath1, Jonathan Pletcher2, Christine Forke2, and Scott Schmid3. (1) Philadelphia Department of Public Health, 500 South Broad Street, VASP, 2nd Floor, Philadelphia, PA, USA, (2) The Children's Hospital of Philadelphia, Philadelphia, PA, USA, (3) Centers for Disease Control and Prevention, Atlanta, GA, USA


BACKGROUND:
Recommendations for varicella vaccine use have exempted individuals with reliable histories of disease from receiving the vaccine since licensure in 1995. Varicella among these exempted individuals may be occurring more frequently post-vaccine-licensure due to inaccurate recall or misdiagnosis.

OBJECTIVE:
To examine the validity of reported varicella history as a measure of Varicella Zoster Virus (VZV) immunity among unvaccinated urban residents aged 1 to 29 years.

METHOD:
As part of a cross-sectional study, unvaccinated individuals aged 1 to 29 years were enrolled at community-based sites in Philadelphia. Study staff interviewed participants or their parents/guardians to collect reported varicella history and demographic characteristics. A serologic specimen was obtained from each participant and tested for VZV IgG antibody at the CDC National VZV Laboratory. The sensitivity, specificity, and positive predictive value (PPV) of reported varicella history with 95% confidence intervals were examined for five age groups.

RESULT:
To date, 427 participants have been enrolled. VZV susceptibility rates by age group were 98.6% (1-4 years), 18.8% (5-9 years), 16.7% (10-14 years), 4.2% (15-19 years), and 2.9% (20-29 years). Parents of two 1-4 year olds reported positive histories; however, both children were susceptible. Among those 5-9 years, sensitivity of reported history was 84.6% (54.6%-98.1%), specificity was 66.7% (9.4%-99.2%), and PPV was 91.7% (61.5%-99.8%). For 10-14 year olds, sensitivity was 81.3% (71.0%-89.1%), specificity was 18.8% (0.0%-37.9%), and PPV was 83.3% (73.2%-90.8%). PPV was high (>98%) for those 15-19 years and 20-29 years.

CONCLUSION:
Preliminary analyses suggest reported varicella history is no longer a strong indicator of VZV immunity among unvaccinated children and younger adolescents. Data collection and analyses will continue to assess whether modifications to varicella vaccination screening practices are needed to ensure all susceptible children and adolescents are offered vaccine.

LEARNING OBJECTIVES:
To describe the validity of reported varicella history as a measure of VZV immunity post-vaccine-licensure.

See more of Epidemiology Track Workshop: Progress with Varicella Surveillance
See more of The 39th National Immunization Conference (NIC)