The differences in short- and long-term varicella-zoster virus (VZV) immunoglobulin G levels following varicella vaccination of healthcare workers measured by VZV fluorescent-antibody-to-membrane-antigen assay (FAMA), VZV time-resolved fluorescence immunoassay and a VZV purified glycoprotein enzyme immunoassay

Healthcare workers (HCWs) reporting no history of varicella frequently receive varicella vaccination (vOka) if they test varicella-zoster virus (VZV) immunoglobulin G (IgG) negative. In this study, the utilities of VZV-IgG time-resolved fluorescence immunoassay (VZV-TRFIA) and a commercial VZV-IgG purified glycoprotein enzyme immunoassay (gpEIA) currently used in England for confirming VZV immunity have been compared to the fluorescent-antibody-to-membrane-antigen assay (FAMA). A total of 110 HCWs received two doses of vOka vaccine spaced 6 weeks apart and sera collected pre-vaccination (n = 100), at 6 weeks post-completion of vaccination (n = 86) and at 12-18 months follow-up (n = 73) were analysed. Pre-vaccination, by FAMA, 61.0% sera were VZV IgG negative, and compared to FAMA the sensitivities of VZV-TRFIA and gpEIA were 74.4% [95% confidence interval (CI) 57.9-87.0] and 46.2% (95% CI 30.1-62.8), respectively. Post-completion of vaccination the seroconversion rate by FAMA was 93.7% compared to rates of 958% and 708% determined by VZV-TRFIA and gpEIA, respectively. At 12-18 months follow-up seropositivity rates by FAMA, VZV-TRFIA and gpEIA were 78.1%, 74.0% and 47.9%, respectively. Compared to FAMA the sensitivities of VZV-TRFIA and gpEIA for measuring VZV IgG following vaccination were 96.4% (95% CI 91.7-98.8) and 74.6% (95% CI 66.5-81.6), respectively. Using both FAMA and VZV-TRFIA to identify healthy adult VZV susceptibles and measure seroconversion showed that vOka vaccination of HCWs is highly immunogenic.