Varicella-Zoster Virus Antibody, IgG
The Varicella-Zoster Virus IgG antibody test detects circulating IgG antibodies to VZV in serum, confirming immunity from prior natural infection or vaccination. It is indicated for pre-vaccination immunity screening, occupational health assessment in healthcare workers, pre-immunosuppression and transplant candidate evaluation, and susceptibility assessment in pregnant women and immunocompromised patients following VZV exposure.
1
Biomarkers
Blood (serum)
Sample
2–4 business days
Turnaround
No
Fasting
What is the VZV IgG test?
The Varicella-Zoster Virus Antibody, IgG test detects circulating IgG antibodies to VZV in serum, providing a serological determination of immune status against varicella and zoster. It is ordered to establish whether a patient has immunity from prior natural infection or completed vaccination — information that directly informs vaccination decisions, exposure management protocols, and pre-treatment safety assessments. The assay is qualitative in standard format (positive / equivocal / negative), with seropositivity indicating established humoral immunity and seronegativity indicating susceptibility requiring clinical action. Within the infectious disease serological landscape, VZV IgG is the first-line and universally available marker for immunity assessment and stands alone in clinical utility for this indication. VZV IgM is the complementary marker for suspected acute primary infection, not immunity screening; the two assays serve distinct clinical purposes and should not be substituted for one another. Where more precise quantitative titer data is required — as in transplant immunology or immunodeficiency workup — the fluorescent antibody to membrane antigen (FAMA) assay is the research-grade reference method, though it is not routinely available through commercial networks. For the vast majority of clinical applications — occupational health, pre-vaccination screening, pre-immunosuppression workup — VZV IgG via standard EIA is the appropriate and validated test.
What does the VZV IgG test measure?
Varicella-zoster virus is a neurotropic alphaherpesvirus that causes varicella (chickenpox) on primary infection before establishing lifelong latency in dorsal root, trigeminal, and autonomic ganglia. IgG antibodies to VZV emerge 2–4 weeks after primary infection and persist indefinitely in immunocompetent individuals, conferring protective immunity against reinfection. Vaccine-induced IgG titres develop following the live attenuated varicella vaccine series but are generally lower than those generated by natural infection, with the same serological marker used to assess both sources of immunity. The structural glycoproteins gE, gB, and gI are the principal antigenic targets of the humoral immune response.
VZV IgG seropositivity confirms prior exposure to the virus — through natural infection or vaccination — and is the standard serological indicator of immunity used in clinical and occupational health practice. Seronegative results identify susceptible individuals who are candidates for vaccination or, following exposure, post-exposure prophylaxis with varicella-zoster immune globulin (VariZIG). In immunocompromised patients, the assay retains diagnostic utility but seronegative results must be interpreted cautiously, as impaired humoral immunity can suppress antibody production below the detection threshold even in individuals with prior exposure. The assay does not differentiate between infection-derived and vaccine-derived immunity.
Why is the VZV IgG test ordered?
- Pre-vaccination immunity screening — confirming susceptibility before administering varicella or zoster vaccine, particularly in adults without documented vaccination history or reliable recollection of prior chickenpox illness
- Healthcare worker occupational health programmes — establishing VZV immune status as a condition of employment or clinical placement, in line with infection prevention requirements for direct patient contact roles
- Pre-immunosuppression assessment in transplant candidates and patients commencing biologic therapy, chemotherapy, or high-dose corticosteroids — identifying susceptible individuals who require vaccination before immune competence is pharmacologically reduced
- Exposure assessment in susceptible pregnant women — quantifying serological risk following VZV contact to guide post-exposure prophylaxis decisions with VariZIG and inform obstetric management
- Post-vaccination serology confirmation in immunocompromised patients or high-risk populations where vaccine seroconversion cannot be assumed and documented immune response is clinically required
- Evaluation of susceptibility in neonates, infants, or paediatric patients with no vaccination history where maternal antibody transfer status is clinically relevant
- Investigation of atypical zoster presentations or dermatomal rashes in immunocompromised patients where clinical diagnosis is uncertain and serological context is required alongside VZV PCR
- Occupational exposure management and contact tracing protocols in healthcare, childcare, or residential care settings following confirmed varicella index cases
Sample collection and turnaround
Sample type
Blood (serum)
Fasting required
No
Collection method
Phlebotomy at Access Med Labs draw site
Turnaround
2–4 business days
Collection notes
Standard venipuncture into a serum separator tube (SST / gold top). No special preparation or fasting required. Practitioners should document any recent varicella or zoster vaccination, IVIG administration, or VariZIG treatment relative to collection date, as these significantly affect result interpretation. No centrifugation or special light-protection requirements apply to this analyte. # REVIEWER FLAG: Confirm exact tube type, minimum volume, and any special handling requirements with Access Med Labs specimen collection guidelines before publication.
Specimen requirements
Minimum 1.0 mL serum. Allow specimen to clot at room temperature; centrifuge and separate serum within 2 hours of collection. Serum is stable at 2–8°C for up to 7 days and at −20°C for longer-term storage. # REVIEWER FLAG: Confirm stability data and minimum volume with Access Med Labs assay documentation.
What can affect VZV IgG results?
The live attenuated varicella vaccine stimulates VZV IgG production, producing a positive serological result that is indistinguishable from infection-derived immunity by standard EIA. Practitioners should document vaccination history relative to specimen collection when the purpose is distinguishing infection from vaccination status.
IVIG and varicella-zoster immune globulin preparations contain passively transferred VZV IgG antibodies from pooled donor serum. Administration within the preceding weeks to months can produce transient seropositivity that does not reflect endogenous immune status. Timing of administration relative to specimen collection must be documented.
Impaired B-cell function — from pharmacological immunosuppression, haematological malignancy, HIV, or primary antibody deficiency — can suppress VZV IgG production below the assay detection threshold despite prior viral exposure or vaccination. Seronegative results in immunocompromised patients may underestimate true prior exposure and should be interpreted alongside clinical and vaccination history.
IgG class switching and seroconversion following primary varicella infection typically occurs 2–4 weeks after symptom onset. Specimens collected during the acute phase or early convalescence may return negative or equivocal IgG results despite active infection. Paired acute and convalescent serology or VZV PCR is more appropriate in this context.
Antigenic homology between VZV and other herpesviruses — particularly HSV-1 and HSV-2 — is low at the glycoprotein level for modern EIA platforms, making clinically significant cross-reactivity uncommon. However, older or lower-specificity assay platforms may produce equivocal results in the context of high-titre HSV infection. # REVIEWER FLAG: Confirm Access Med Labs assay specificity data and cross-reactivity profile before publication.
Significant haemolysis or severe lipemia can interfere with optical density readings in EIA-based platforms, potentially producing equivocal or erroneous results. Access Med Labs specimen rejection criteria should be consulted when sample quality is suboptimal. # REVIEWER FLAG: Confirm rejection criteria with Access Med Labs laboratory documentation.
What do VZV IgG results mean?
Elevated
A positive VZV IgG result (index ≥1.10 or above laboratory-specific cut-off) indicates established humoral immunity to varicella-zoster virus from prior natural infection or completed vaccination. In the context of immunity screening, this result confirms protection and vaccination is not indicated. Practitioners should note that very high titres do not provide additional clinical information in routine screening; quantitative interpretation is reserved for immunocompromised patient monitoring where protective titre thresholds may be relevant.
Normal
An equivocal result (index 0.90–1.09) is indeterminate and does not reliably confirm or exclude immunity. Clinical management should not be based on an equivocal result alone. Repeat testing in 2–4 weeks is recommended in immunocompetent patients. In high-risk scenarios (immunosuppressed, pregnant, pre-transplant), clinical judgement should lean toward treating the patient as susceptible pending confirmatory serology.
Reduced
A negative VZV IgG result (index <0.90) indicates absence of detectable circulating antibodies and serological susceptibility to varicella. In immunocompetent individuals, this confirms no prior exposure or vaccination and identifies the patient as a candidate for the varicella vaccine series. In pregnant women and immunocompromised patients, a negative result following known exposure warrants urgent consideration of post-exposure prophylaxis with VariZIG. In immunosuppressed patients, a negative result does not exclude prior exposure — see caveats.
Note: The most clinically significant interpretive limitation is the potential for false-negative results in immunosuppressed patients — including transplant recipients, patients on biologics or high-dose corticosteroids, and those with HIV-related immunosuppression — who may have had prior VZV exposure but lack adequate antibody production to exceed the assay threshold. Vaccination and exposure history must be integrated with serological findings in this population. Additionally, the assay cannot distinguish between infection-derived and vaccine-derived IgG, nor can it reliably differentiate between latent VZV (past infection, no active disease) and recent reactivation; VZV PCR from lesion swab or CSF is the appropriate test for active disease investigation.
Frequently asked questions
VZV IgG measures long-term antibodies that indicate established immunity from prior infection or vaccination. VZV IgM is an acute-phase marker that rises during primary varicella infection and early reactivation. IgG is the appropriate test when the clinical question is immune status; IgM is ordered when acute primary infection is suspected.
How to access the VZV IgG test
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Published: May 22, 2026
Last reviewed: May 22, 2026
- Marin M, et al. Prevention of Varicella: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. (2007)
- Gershon AA, et al. Varicella zoster virus infection. Nat Rev Dis Primers. (2015)
- Oxman MN, et al. A vaccine to prevent herpes zoster and postherpetic neuralgia in older adults. N Engl J Med. (2005)
- Levin MJ. Immune senescence and vaccines to prevent herpes zoster in older persons. Curr Opin Immunol. (2012)
This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.