334. Measurement of Varicella (VZ) Cell Mediated Immune (CMI) Response in Varicella Vaccinated Health Care Workers (HCWs) Lacking VZ ELFA/VZ ACIF Serological Response
Session: Poster Abstract Session: HAI: Occupational Health
Thursday, October 8, 2015
Room: Poster Hall
Posters
  • 334_IDWPOSTER.pdf (328.5 kB)
  • Background: Demonstration of serologic immunity to VZ is essential for patient and employee safety in a hospital setting. VZ Enzyme-Linked Fluorescent Assay (ELFA) is currently the traditional methodology for measuring VZ immunity in this setting.   However, while VZ ELFA antibody has high positive predictive value for protection, it has a poor negative predictive value.   Although better, VZ Anti-Complement Immunofluorescence (ACIF) assay is similarly problematic. To improve this, VZ ELFA, VZ ACIF, and VZ CMI responses were evaluated in HCWs who remained VZ ELFA/ACIF negative after 2 or more doses of varicella vaccine.

    Methods: HCWs who had previously been vaccinated with VZ vaccine then had VZ ELFA, VZ ACIF, and VZ CMI testing all done on the same blood specimen. VZ ELFA was performed by Focus Technologies (Cypress, CA) and VZ ACIF by bioMérieux Vitek, Inc. (Hazelwood, MO).  CMI response was measured by lymphocyte transformation assay. Positive and negative results are determined by comparison to internal controls. HCWs completed a survey relating to prior VZ exposures.

    Results:   In 2014 10 HCWs were identified according to the parameters above. Male = 5; Female = 5. Mean age = 42.5 years; Median = 42 years; Range = 24-63. 
    HCW # 1 2 3 4 5 6 7 8 9 10    TOTAL
    VZ ELFA Neg Neg Neg Neg Neg Neg Neg  Equiv Equiv Neg    2 E/8 N
    VZ ACIF Neg Neg Neg Pos Pos Neg Neg  Neg Pos Neg    3 P/7 N
    VZ CMI Neg Pos Pos Pos Pos Pos Pos Pos Pos Pos    9 P/1 N
    VZ Exposed Yes Yes Yes No Yes Yes No Yes Yes Yes    8Yes/2No

    Survey results revealed that only one HCW was born and raised in the tropics (Jamaica). Eight of 10 grew up with siblings, 4 of whom had varicella. Four of 10 have children of their own – none have had varicella. Six of 10 have been repeatedly exposed to patients with varicella and/or shingles – none developed clinical varicella.

    Conclusion: In this small selective sample of previously vaccinated HCWs, serological evidence of immunity to VZ by the ELFA method remained difficult to demonstrate while VZ CMI responsiveness was present in 9 of 10 tested suggesting that they have recall to the VZ antigen.  Exactly what that means in terms of protective immunity remains unclear. We will follow up and track the future clinical, serological, and CMI responses of these HCWs to exposures to  VZ to more precisely define the role of CMI responsiveness .

    Arthur E. Brown, MD, FIDSA, FSHEA1, William J. Schneider, MD, MPH1, Yi-Wei Tang, MD PhD, FIDSA2, Sulin Low, RN, COHN1, Peter Maslak, MD2, Katherine Smith, BS2 and Luz Gomez, MPH M(ASCP)2, (1)Employee Health & Wellness Services, Memorial Sloan Kettering Cancer Center, New York, NY, (2)Laboratory Medicine, Memorial Sloan Kettering Cancer Center, New York, NY

    Disclosures:

    A. E. Brown, None

    W. J. Schneider, None

    Y. W. Tang, None

    S. Low, None

    P. Maslak, None

    K. Smith, None

    L. Gomez, None

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