Live varicella immunization in healthy non-immune nurses.

Thirty-four varicella-zoster virus (VZV) seronegative nurses were vaccinated with the live varicella vaccine (Varilrix) and followed for periods of up to 36 months. No major vaccine reactions were observed. At 5 and 12 months, 94% of the nurses had seroconverted but at 3 years, only 64% retained antibody activity. However, lymphocyte transformation to VZV antigen was positive in 7 seronegative nurses, all of whom had previously seroconverted. The one nurse who developed chickenpox had not seroconverted after vaccination. Two out of 11 seroconverted nurses had a subclinical reinfection, as shown by a rise in antibody, upon exposure to varicella. In contrast, 4 out of 5 seronegative nurses who had refused vaccination developed chickenpox. Varilrix is therefore safe, immunogenic, and protective in adults and can be considered for routine use in susceptible health workers. However, it is still uncertain whether lifelong immunity is obtained with this vaccine. Both cell-mediated and antibody tests are needed for long-term assessment of immunity to chickenpox.