Clinical reinfection with varicella-zoster virus.

Eight patients became clinically reinfected with varicella-zoster virus despite the presence of specific antibody in the blood three days to six months before the onset of illness. One patient had had varicella previously; a second had been immunized with live, attenuated varicella vaccine 10 months earlier. While it was suspected that these patients experienced a reactivation of latent virus that caused atypical disseminated zoster rather than varicella, detailed study of the vaccinated child suggests that this was not the case; by restriction-endonuclease techniques, this vaccinee was shown to have been infected with wild-type varicella-zoster virus despite the presence of specific antibody and cellular immunity to the virus. All cases clinically resembled chickenpox. Thus, not only subclinical varicella (manifested by a rise in antibody titer after close exposure) but also clinical reinfection with the virus can occur. Clinical reinfection probably develops more frequently in immunocompromised than in immunocompetent individuals. Reinfections are usually mild.