Seroprevalence of varicella antibodies among pregnant women in Lyon-France.

The purpose of the study was to calculate the seroprevalence of immunity to the varicella-zoster virus (VZV) infection and to evaluate the positive predictive value (PPV) and the negative predictive value (NPV) of the self-reported history of VZV infection in pregnant women. A cross sectional study was conducted in 18 private medical analysis laboratories. Information on socio-demographic characteristics and past history of varicella or zoster were collected using a questionnaire. Blood samples were obtained to determine the serological levels of past exposure to VZV. Overall, 486 pregnant women were recruited. The seroprevalence of VZV antibodies was 98.8%. Six women were seronegative, of whom four were primiparous. The PPV was high (99.5%) while the NPV was only 10.3%. The PPV is a reliable marker of prior VZV infection. In contrast, a negative history does not predict lack of immunity and should be completed by serological analysis which might be introduced to routine antenatal blood tests.