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EBV viral capsid antigen (VCA) IgG

An antibody to Epstein-Barr virus that appears in a first infection and then stays for life, so it shows whether you have ever been infected.

AI-verified against cited sources. Awaiting expert reviewAlso called VCA IgG, EBV VCA IgG, anti-VCA IgGLOINC 24114-1

What it is

Epstein-Barr virus (EBV) is a very common virus that causes infectious mononucleosis (mono) in some people. VCA stands for viral capsid antigen, a protein in the shell of the virus. Your body makes IgG antibodies against it early in an infection, and they usually stay for life. The result is reported as negative, equivocal or positive, and many labs also print a number.

Why it matters

VCA IgG tells a clinician whether you have ever met EBV. A negative result usually means you have not been infected yet, so you could still catch it. A positive result means a current or past infection. The CDC says more than 90% of adults have been infected, so a positive result is the usual finding. To tell a recent infection from an old one, VCA IgG is read together with VCA IgM and EBNA IgG.

If it’s high

A positive VCA IgG means you have been infected with EBV at some time, either recently or long ago. By itself it cannot say when. The CDC says high or rising VCA IgG with no EBNA antibodies, after at least 4 weeks of illness, points to a recent infection. VCA IgG together with EBNA IgG suggests a past infection.

Common causes

  • An EBV infection in the past, often in childhood and often without symptoms
  • A recent first infection such as mono
  • Reactivation of an old EBV infection, which can show several antibody types at once

What can help

  • Ask your clinician to read this result together with VCA IgM and EBNA IgG
  • Tell your clinician when your symptoms began, because timing matters for these tests

What can affect your result

  • Timing: VCA IgG is usually already positive when symptoms start
  • The lab's kit and cut-offs: results from different manufacturers are not interchangeable
  • An equivocal result may be repeated in 10 to 14 days
  • Labs use different kits and cut-offs. ARUP notes that EBV IgG values from different manufacturers' methods may not be used interchangeably.
  • The size of the number does not show how recent the infection is. ARUP notes that the reported level cannot be correlated to an endpoint titer.

Usually already present when symptoms start (Quest), peaks about 2 to 4 weeks after symptoms begin, then persists for life (CDC).

When to talk to a clinician

A VCA IgG result on its own is not urgent. Talk with a clinician about a fever, sore throat, swollen glands or tiredness that does not go away. Get urgent care for trouble swallowing or breathing, or sudden severe belly pain, especially on the upper left side. If you cannot breathe well, call 911 or your local emergency number.

Questions you could ask

  • Which EBV tests should be read together for my situation?
  • Was my blood drawn at a point where these tests are reliable?
  • Does my VCA IgG, together with my other EBV results, point to a recent or a past infection?
  • Do I need any follow-up testing?

Questions people ask

My VCA IgG is positive but EBNA IgG is negative. What does that mean?

It can fit a recent infection, because EBNA appears slowly, 2 to 4 months after symptoms start. It can also happen with a past infection in some people. Your clinician looks at the VCA IgM result, your symptoms and the timing, and may add other tests.

Does a higher number mean a more recent or worse infection?

Not necessarily. ARUP notes that the reported level cannot be correlated to an endpoint titer, and numbers from different labs cannot be compared. The pattern across the EBV tests and your symptoms matter more.

Show the science and sources

For clinicians and researchers

VCA IgG is measured by immunoassay. Quest reports U/mL with under 18.00 negative, 18.00 to 21.99 equivocal and over 21.99 positive; ARUP (semi-quantitative chemiluminescent immunoassay) reports 17.9 U/mL or less not detected, 18.0 to 21.9 indeterminate (repeat in 10 to 14 days may help) and 22.0 U/mL or more detected; Mayo reports negative or positive by ELISA. Per Quest, VCA IgG is typically detectable at clinical presentation and persists for life, and its absence usually indicates susceptibility. Per the CDC it peaks 2 to 4 weeks after symptom onset and persists. VCA IgM with VCA IgG and no EBNA IgG indicates acute infection, and VCA IgG with EBNA IgG and no VCA IgM is typical of past infection; however, VCA IgG alone can reflect acute or past infection, and all three markers can appear together in recent infection or reactivation (De Paschale and Clerici 2012). The CDC notes that paired acute and convalescent sera are not useful for separating recent from past infection. The magnitude of a VCA IgG value cannot be correlated to an endpoint titer (ARUP). Immunofluorescence titers are still reported by some labs.

LOINC 24114-1 (primary), 7885-7, 5157-3, 30339-6, 20490-9. Specimen: serum.

Sources

  1. Laboratory Testing for Epstein-Barr Virus (EBV), US Centers for Disease Control and Prevention
  2. About Epstein-Barr Virus (EBV), US Centers for Disease Control and Prevention
  3. Epstein-Barr Virus Viral Capsid Antigen (VCA) Antibody (IgG) (test code 8474), Quest Diagnostics
  4. Epstein-Barr Virus Antibody to Viral Capsid Antigen, IgG (test 0050235), ARUP Laboratories
  5. Epstein-Barr Virus Antibody Profile, Serum (test EBVAB), Mayo Clinic Laboratories (via testcatalog.org)
  6. Serological diagnosis of Epstein-Barr virus infection: Problems and solutions, World Journal of Virology (2012)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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