Delayed hypersensitivity skin test to detect susceptibility to varicella and zoster

A crude varicella skin-test antigen corresponding to an inactivated partly-purified high-titre varicella Oka-strain vaccine was prepared at Smith Kline-RIT. It was used for a delayed hypersensitivity skin test in 60 healthy adults for determination of their immune status. The findings were analysed according to the presence or absence of humoral antibodies to varicella-zoster virus (VZV), and of a specific cell-mediated immune (CMI) response as measured by the VZV-specific lymphocyte transformation test. The immune status to varicella could be determined in all subjects provided that the amount of antigenic material in the skin-test antigen was sufficiently high. The 2 tests for the CMI response, the delayed hypersensitivity skin test and the lymphocyte transformation test, gave concordant results in both seropositive and seronegative individuals. The inactivated skin-test antigen cannot replace vaccination with the live varicella vaccine since it is unable to induce seroconversion in seronegatives or an antibody booster response in seropositives. Furthermore, seropositive and seronegative subjects showing a negative response to the varicella-zoster-specific lymphocyte transformation test remained negative 2 weeks after the injection of the skin-test antigen.