Validity of self-reported varicella disease history in pregnant women attending prenatal clinics

Objective. The purpose of this study was to assess the validity of self-reported history for varicella disease relative to serological evidence of varicella immunity in pregnant women attending antenatal care at clinics located in two diverse geographical locations in the U.S. (Antelope Valley, California, and Philadelphia) with high varicella vaccination coverage. Methods. Pregnant women attending prenatal care appointments who needed blood drawn as part of their routine care were eligible to participate. Self-reported varicella disease history was obtained via questionnaire. Varicella serostatus was determined using a whole-cell enzyme-linked immunosorbent assay to test for varicella zoster virus-specific immunoglobulin G (VZV IgG) antibodies. Results. Of the 309 study participants from Antelope Valley and the 528 participants from Philadelphia who self-reported having had chickenpox disease, 308 (99.7%; 95% confidence interval [CI]: 98.2, 100) and 517 (97.9%; 95% CI: 96.3, 99.0), respectively, had serological evidence of immunity to varicella. Only 6.8% (95% CI: 3.9, 11.0) and 17.4% (95% CI: 13.1, 22.5) of women who self-reported having a negative or uncertain varicella disease history in Antelope Valley and Philadelphia, respectively, were seronegative for varicella antibodies. Conclusion. Despite the dramatic changes in the epidemiology of varicella that have occurred since 1995 due to the introduction and subsequent widespread use of the varicella vaccine, self-reported history of varicella continues to be a strong predictor of VZV IgG antibodies in pregnant women. Negative or uncertain history remains poorly predictive of negative serostatus.