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Vaccine or Virus Serology (IgG Antibody) – Avidity Test

Published: August 9, 2026Updated: August 16, 2026

This test measures how strongly your immune system’s IgG antibodies bind to a specific virus or vaccine antigen, helping assess the timing and strength of your immune response.

Quick summary

["Helps determine if your immune response is recent or long-lasting."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
81119-0
Short code
EBV VCA IgG Avidity Ser IA-Rto
Synonyms
EBV VCA IgG Avidity Ser IA-Rto
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
CPT
82784
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

IgG antibodies are part of your immune system’s defense against infections or vaccines. This test evaluates their *avidity*—how tightly they cling to the antigen (virus or vaccine protein). High avidity suggests a mature, long-term response; low avidity may indicate a recent exposure.

Why It’s Ordered

Doctors may request this test after vaccination (e.g., COVID-19, flu) or exposure to a virus (e.g., hepatitis) to confirm immunity, track progression of infection, or guide treatment decisions.

Sample Collection

A blood sample is drawn from a vein in your arm. The serum portion is tested for IgG antibodies bound to the specific antigen.

Preparation

No special preparation is needed, but avoid strenuous activity 24 hours before testing. If you’re on blood thinners, inform your provider.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

High avidity IgG antibodies suggest a robust, sustained immune response (e.g., months after vaccination). Low avidity may indicate a recent infection or vaccine exposure. This can help differentiate between active immunity (e.g., from vaccination) and passive immunity (e.g., from antibodies transferred post-exposure).

Short name

IgG Antibody Avidity Test

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–3 business days, depending on lab processing times. Your healthcare provider will discuss findings with you.
What does a low avidity result mean?
A low avidity result often means your immune response is still developing, such as shortly after vaccination or infection. It doesn’t necessarily mean you’re not immune—it just indicates the antibodies are still forming.
Can I get this test at home?
No, this test requires a blood sample collected by a healthcare professional in a clinical setting. Some labs offer at-home blood draws, but avidity testing is typically done in a lab.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy