Sèroprèvalence de l’immunité au virus de la varicelle et du zona chez le personnel de crèche et de halte-garderie à Lyon (France)

Objective. - Varicella is a potential occupational hazard for susceptible individuals working in pediatric institutions because infected adults run a greater risk of severe or even fatal varicella and because the disease is so common in children and so contagious. The seroprevalence of varicella-zoster virus (VZV) was examined in a sample of day-care workers in Lyon (France) to determine whether a targeted vaccination policy was needed. Methods. - Two hundred forty-one sera were sampled and analysed with an Elisa test between March and May 2001. Histories of past VZV infection were collected via questionnaires documented either before or after consultation of medical records or other sources of information. Results. - The overall VZV seroprevalence was 99.6%. The positive predictive values of past varicella histories (documented or not) were >99% showing that a history of previous varicella in day-care workers was reliable. However, only 68 to 71% of these with serologically confirmed varicella reported a prior history of varicella. All subjects reporting a non-positive history of varicella were seropositive. Conclusions. - Virtually all day-care workers enrolled in this study presented serological evidence of VZV so that sub-populations at risk for varicella infection for which VZV vaccination may be effective could not be identified. However, the VZV seroprevalence of the workers in pediatric institutions being presumably higher than that of the general adult population (94-96.3%), vaccination of susceptible young recruits before any exposure to the VZV, or even vaccination of students willing to work in a pediatric institution, may be positive.