Breakthrough varicella in a cancer patient with persistent varicella antibody after one varicella vaccination.

A boy with Hodgkin disease contracted breakthrough varicella from his father, who had chickenpox. The boy had received a single varicella vaccination and was seropositive by enzyme-linked immunosorbent assay before being diagnosed with breakthrough varicella. Seropositivity after a single varicella vaccination does not guarantee complete protection in an immunocompromised child.