Background Primary varicella infection is caused by varicella-zoster virus (VZV). It is a common childhood infection, which is usually benign but can occasionally cause morbidity and mortality. In immunosuppressed adults, atypical presentation and disseminated disease can occur with significant morbidity and mortality. A VZV vaccine is available.
Objectives This study was designed to measure the prevalence of immunity to VZV and to determine the predictive value of a self-reported history of varicella infection in a population of dermatological patients receiving systemic immunosuppressant therapy. We sought to assess the need for routine serological testing for varicella-zoster immunity in this cohort.
Methods Serological testing for VZV immunity was done on 228 patients receiving systemic immunosuppressive treatment for a dermatological condition. Information regarding a history of previous primary VZV infection was obtained from each patient.
Results Two hundred and twenty-eight patients had VZV serology performed. The mean age of the patients was 49·6 years. The prevalence of VZV seropositivity in this cohort was 98·7%. One hundred and two patients (44·7%) reported having a definite history of primary VZV. The sensitivity of a self-reported history of VZV infection was 45·3% with a specificity of 100%. The positive and negative predictive values of a self-reported history of VZV for serologically confirmed immunity were 100% and 2·3%, respectively.
Conclusions The prevalence of VZV IgG antibodies in our cohort of Irish dermatology patients receiving immunosuppressive therapy is 98·7%. A recalled history of varicella infection is a good predictor of serological immunity. This study has shown that there are VZV-susceptible individuals within our cohort. These patients did not have a clear history of previous infection. We recommend serological testing of patients without a clear history of infection prior to the commencement of immunosuppressive therapy and vaccination of patients with negative serology.