Varicella-zoster virus (VZV) IgG
A blood test for IgG antibodies to the chickenpox virus, used to check for evidence of past infection or vaccination.
AI-verified against cited sources. Awaiting expert reviewAlso called VZV IgG, VZV-IgG, VZV Ab IgGLOINC 5403-1
What it is
VZV is the virus that causes chickenpox, and later in life it can cause shingles. After chickenpox or the vaccine, your immune system makes antibodies called IgG. This test looks for them in your blood. A positive result shows the antibodies are there, which usually reflects past infection or vaccination. It does not show whether you have an infection right now.
Why it matters
Chickenpox is usually mild in children but can be serious in adults, pregnant women, newborns and people with weakened immune systems. A VZV IgG result is often used to check for evidence of immunity, for example in early pregnancy, before some treatments, or for health care work. The CDC accepts lab evidence of immunity as one proof. A written record of 2 doses of vaccine takes priority over a later blood test.
If it’s low
Negative means the test did not find VZV IgG. It can mean you have not had chickenpox or the vaccine. It can also happen after vaccination, because the CDC notes that commercial tests miss some antibody made by the vaccine, so you may still be protected. A written record of 2 vaccine doses counts over a negative blood test.
Common causes
- Never having had chickenpox or the vaccine
- Antibody levels after vaccination that are too low for the test to detect
- Testing very early in a first infection, before antibody shows up
What can help
- Look for your vaccination records
- Ask your clinician whether chickenpox vaccination is right for you, since it is recommended for adults without evidence of immunity
- If you are pregnant or may become pregnant, ask your clinician about timing
If it’s high
Positive means VZV IgG antibodies were found. This is the usual result for adults. In tests done in 1998 and 1999, 96 to 97% of US-born adults aged 20 to 29 and 97 to 99% of those 30 and older had evidence of immunity. A positive result alone does not show whether you are sick now. If you have a new blistering rash, your clinician can tell you which tests apply.
Common causes
- Past chickenpox, including a mild or forgotten case
- Chickenpox vaccination
- Past shingles, which is caused by the same virus
- Rarely, a current chickenpox or shingles infection when you also have symptoms
What can help
- Keep your vaccination records and share this result with your clinician
- Ask whether a positive result is enough for what you need it for, such as work, school or pregnancy planning
What can affect your result
- Vaccination: commercial tests can miss low antibody levels after the vaccine
- The kit your lab uses: units, cutoffs and the width of the equivocal zone differ between labs
- Age and place of birth: most adults have been infected or vaccinated
- Very recent infection: antibody may not have appeared yet
- Commercial IgG tests are not sensitive enough to detect all antibody made after vaccination, so a negative result after vaccination does not mean you are unprotected (CDC, Labcorp).
- Every lab uses its own kit, units and cutoffs. Labcorp's immunoassay reports an index (negative below 135, equivocal 135 to 165, positive above 165), and other labs' numbers are not comparable.
- Latex agglutination methods can give false-positive results (CDC Pink Book).
IgG is made in the weeks after chickenpox or a vaccine, and most adults stay positive for years (96 to 99% of US-born adults tested in 1998 and 1999). One result is usually enough.
When to talk to a clinician
Contact a clinician promptly if your result is negative or you are unsure of your immunity and you have been around someone with chickenpox or shingles, especially if you are pregnant, have a weakened immune system, or live with or care for a newborn. A new itchy blistering rash with fever, or a painful blistering rash on one side of the body, also needs prompt attention.
Questions you could ask
- Do I need any other immunity checks, such as measles, mumps or rubella?
- Does this result count as evidence of immunity for what I need it for?
- Do my vaccine records count instead of this blood test?
- Which of my vaccines are up to date, including chickenpox?
- What should I do if I am around someone with chickenpox or shingles?
Questions people ask
I had the chickenpox vaccine. Why is my VZV IgG negative?
Commercial IgG tests are built to pick up the antibody level that follows natural infection, and they can miss the lower level that follows vaccination. The CDC says a record of 2 vaccine doses counts over a later negative test. Bring your vaccine record to your clinician.
Does a positive VZV IgG mean I have chickenpox or shingles now?
No. A positive IgG usually reflects a past infection or vaccination. A current infection is judged from symptoms such as a blistering rash, and clinicians can confirm it with a PCR test on a swab from a blister.
What does an equivocal result mean?
It means the result fell between the lab's negative and positive cutoffs, so the test could not say clearly. Your clinician may repeat the test, use another test or rely on your vaccine records.
Show the science and sources
For clinicians and researchers
VZV IgG is measured by immunoassay. In Labcorp test 096206 (chemiluminescent immunoassay, result LOINC 5403-1) an index below 135 is negative, 135 to 165 is equivocal and above 165 is positive. Other labs use different assays, units and cutoffs, so values are not interchangeable. The CDC Pink Book states that commercially available serologic IgG tests are not sufficiently sensitive to detect the low antibody levels that follow vaccination, that routine testing after 2 vaccine doses is not recommended, and that documented receipt of 2 doses supersedes later serology. After one dose, about 97% of children aged 12 months through 12 years develop detectable antibody, and about 99% of adolescents and adults do after a second dose. Acceptable evidence of immunity includes age-appropriate vaccination records, lab evidence of immunity or confirmed disease, and a provider diagnosis of varicella or herpes zoster. Birth in the US before 1980 is accepted for most adults, but not for health care personnel, pregnant women or immunocompromised people. IgM commercial kits lack sensitivity and specificity, and PCR is the most helpful test to confirm a current case.
LOINC 5403-1 (primary), 8047-3, 19162-7, 15410-4, 22602-7. Specimen: serum.
Sources
- Epidemiology and Prevention of Vaccine-Preventable Diseases: Varicella, Centers for Disease Control and Prevention
- Clinical Overview of Chickenpox (Varicella), Centers for Disease Control and Prevention
- Varicella Vaccine Recommendations, Centers for Disease Control and Prevention
- Chickenpox and Shingles Tests, MedlinePlus (U.S. National Library of Medicine)
- Varicella-Zoster Virus (VZV) Antibodies, IgG (test 096206), Labcorp
- Varicella-Zoster Virus (VZV) IgG, Immunity Status (test 096010), Labcorp
- LOINC codes verified with the NLM Clinical Tables LOINC search (e.g. 5403-1), U.S. National Library of Medicine
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.