Susceptibility to varicella-zoster virus in applicants for nurse training in Scotland

We investigated the immunity to varicella-zoster virus (VZV) of a cohort of applicants for nurse training and determined the relationship between immune status and history of chickenpox or shingles based on a self-completed questionnaire. Three hundred and fifty-six applicants for nurse training were enrolled at an occupational health department in NHS Scotland and 96% were immune to VZV. The positive predictive value of a history of VZV infection for seropositivity was 98% (286/292). The negative predictive value was 14% (9/64). History of chicken pox/shingles had a sensitivity of 84% (286/341) and specificity of 60% (9/15). Screening using past clinical history compatible with VZV infection would have missed 40% of those possibly susceptible to VZV on the basis of the ELISA IgG test. We conclude absence of past history of chickenpox or shingles is an unreliable identifier of susceptibility to VZV in healthcare workers. The Control of Substances Hazardous to Health (COSHH) Regulations 1999 require employers to make effective vaccines available for those employees who are not already immune to a biological agent to which they are exposed or liable to be exposed. Serological testing of healthcare workers would better identify those who are susceptible to VZV infection.