Immunity and viral serology . Patient guide
Varicella immunity (VZV IgG) Blood Test
Also known as: Chickenpox immunity, Varicella zoster antibodies, VZV antibody test
What is VZV IgG
Varicella zoster IgG measures the protective antibody response to the varicella zoster virus, which causes chickenpox in childhood and shingles (zoster) in adulthood. It is most commonly checked in healthcare workers, in pregnant patients after a possible exposure, and before immunosuppressive therapy.
This biomarker entry is being clinically reviewed by our team. The factual content draws on UK guidance (NICE, NHS, Royal Colleges and the relevant speciality society where cited).
Reference range
Reported in IU/mL (lab-specific cut-off, usually around 100 to 165 mIU/mL). Final reports always carry the issuing laboratory's range, which is what your clinician will interpret against.
| Group | Range | Note |
|---|---|---|
| Non-immune (negative or equivocal) | IgG below lab cut-off | Vaccination considered (depending on indication and patient context) |
| Immune (positive) | IgG above lab cut-off | Protective immunity from past chickenpox or vaccination |
What it is
Varicella zoster IgG is a specific antibody made after natural chickenpox infection (still the most common reason for immunity in UK adults, as routine childhood varicella vaccination has only recently been added to the UK schedule following JCVI advice) or after the varicella vaccine. A positive IgG indicates long-term protection against severe disease. Most UK adults are IgG-positive even when they do not recall having had chickenpox.
Why a clinician would order it
VZV IgG is requested in healthcare workers as part of occupational health, in pregnant patients who have been in contact with a confirmed case of chickenpox or shingles (so that immunoglobulin can be given urgently if non-immune), before starting immunosuppressive medication, and in patients about to undergo organ transplantation. It is also occasionally requested as part of a general immunity work-up.
What your VZV IgG result means
Laboratory reports use different wording for the same result. Here is what each one means. This is general information, not a personal interpretation: a GMC-registered clinician should review your result against your history.
Varicella (VZV) IgG reactive / positive / detected
Protective antibodies to the varicella zoster virus were found, so you are immune to chickenpox, almost always from past infection (even if you do not remember having chickenpox) or from vaccination. "Reactive", "positive" and "detected" mean the same thing: long-term protection against severe disease. Most UK adults are IgG-positive.
Varicella (VZV) IgG non-reactive / negative / not detected
No protective antibodies were found, so you are not currently immune to chickenpox. Depending on your situation (healthcare worker, pre-immunosuppression, pregnancy contact), varicella vaccination or, in pregnancy after exposure, varicella zoster immunoglobulin may be offered. Discuss the right pathway with your clinician.
Varicella (VZV) IgG equivocal / borderline
Your antibody level sits on the laboratory cut-off, so immunity is not clearly established. It is usually treated as non-immune and the test repeated, or vaccination considered depending on your context. An equivocal result does not indicate active chickenpox or shingles.
If your level is outside the range
Symptoms of low VZV IgG
- No symptoms; the implication is no protection if exposed to varicella.
What low can indicate. No immunity to varicella, either from never having had chickenpox or from waning immunity. In a non-pregnant patient the varicella vaccine may be offered (typically two doses, 4 to 8 weeks apart). In a pregnant patient with a recent exposure to chickenpox, urgent specialist input is required.
Symptoms of high VZV IgG
- A positive result is reassuring and carries no symptoms.
What high can indicate. Past chickenpox infection or successful response to vaccination. The patient is protected against future chickenpox, though reactivation of the virus as shingles later in life is still possible.
Testing tips
No fasting required. If recently vaccinated, wait 4 to 6 weeks before testing for immunity. A history of chickenpox in childhood usually correlates with positive IgG, but is not a substitute for the blood test when documentation of immunity is required (for example, before organ transplantation).
Sources
UK guidance our clinicians use when interpreting this marker.
- UK Green Book: Varicella (Chapter 34)
- Royal College of Obstetricians and Gynaecologists: Chickenpox in pregnancy (Green-top 13)
This page is general patient information, not personal medical advice. A GMC-registered clinician will review your results and tailor any interpretation to you. See our Editorial Policy for how we write and review content.
Common questions about VZV IgG
What is a normal VZV IgG range?
Non-immune (negative or equivocal): IgG below lab cut-off (Vaccination considered (depending on indication and patient context)). Immune (positive): IgG above lab cut-off (Protective immunity from past chickenpox or vaccination). Always interpret your own results against the laboratory range printed on your report, since assay-specific reference ranges vary.
What does a low VZV IgG result mean?
No immunity to varicella, either from never having had chickenpox or from waning immunity. In a non-pregnant patient the varicella vaccine may be offered (typically two doses, 4 to 8 weeks apart). In a pregnant patient with a recent exposure to chickenpox, urgent specialist input is required.
What does a high VZV IgG result mean?
Past chickenpox infection or successful response to vaccination. The patient is protected against future chickenpox, though reactivation of the virus as shingles later in life is still possible.
Do I need to fast or prepare for the VZV IgG blood test?
No fasting required. If recently vaccinated, wait 4 to 6 weeks before testing for immunity. A history of chickenpox in childhood usually correlates with positive IgG, but is not a substitute for the blood test when documentation of immunity is required (for example, before organ transplantation).
What does "Varicella (VZV) IgG reactive / positive / detected" mean?
Protective antibodies to the varicella zoster virus were found, so you are immune to chickenpox, almost always from past infection (even if you do not remember having chickenpox) or from vaccination. "Reactive", "positive" and "detected" mean the same thing: long-term protection against severe disease. Most UK adults are IgG-positive.
What does "Varicella (VZV) IgG non-reactive / negative / not detected" mean?
No protective antibodies were found, so you are not currently immune to chickenpox. Depending on your situation (healthcare worker, pre-immunosuppression, pregnancy contact), varicella vaccination or, in pregnancy after exposure, varicella zoster immunoglobulin may be offered. Discuss the right pathway with your clinician.
What does "Varicella (VZV) IgG equivocal / borderline" mean?
Your antibody level sits on the laboratory cut-off, so immunity is not clearly established. It is usually treated as non-immune and the test repeated, or vaccination considered depending on your context. An equivocal result does not indicate active chickenpox or shingles.
Can I order a VZV IgG blood test privately in London?
Yes. WMG Health offers VZV IgG as part of bespoke panels and several pre-built panels at our 134 Harley Street clinic. Results are clinician-reviewed by a GMC-registered doctor within 4 hours for the most common assays. All panels are custom-built around your specific question; bookings via /contact/ or 020 3239 3378.