Varicella serology in institutional exposure management

A resident of a large facility for developmentally disabled persons developed chickenpox, exposing the other residents on his unit prior to diagnosis. Only 4 of the 20 exposed had previous histories. Indirect fluorescent antibody (IFA) testing for varicella-zoster antibodies done on the day the index patient was diagnosed demonstrated protective antibody levels in 18 of 21 residents. These residents returned to habilitative activities earlier than anticipated, maintaining program continuity. We suggest that varicella immunity might be more common in this population than supposed. Cost analysis of laboratory screening versus providing additional staffing during isolation supports screening in similar circumstances.