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 95 8% and 70 8% 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.
Bibliographical noteFunding Information:
This study was funded by the Wellcome Trust grant no. GR075427, J.B. receives additional funding from the NIHR UCL/UCLH Biomedical Research Centre. A.A.G. was in receipt of NIH grant R01-DK093094. We thank Dr Nick Andrews, Statistics, Modelling and Economics Department, Health Protection Directorate, Public Health England, London, for the provision of statistical advice and analysis. We are also grateful to Julianne Brown, Virology Department, Great Ormond Street Hospital, London, for advice on FAMA methodology and the production of Figure 1
© Cambridge University Press 2016.
- VZV glycoprotein EIA
- VZV immunoglobulin G
- VZV time-resolved fluorescence immunoassay
- healthcare workers
- vOka vaccine