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Influenza Virus Antibody Screening (Serum/Plasma)

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

This test checks for antibodies in your blood that may indicate past exposure to the influenza virus, often used to assess immunity after vaccination.

Quick summary

Determines if your immune system has recognized and responded to flu vaccination or natural infection.

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

Key facts at a glance

LOINC
55020-2
Short code
REASONINFLUENZAVIRUSVACCINENOTRECEIVED
Synonyms
—
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
cms-assessment
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

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you’ve had the flu vaccine but still feel unwell, or if you’re unsure whether you’ve been exposed to the flu. It can also help monitor immune response in certain high-risk groups.

What to Expect Before the Test

No special preparation is needed. A blood sample will be taken from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause discomfort. The test itself is quick and done in a lab.

What the Results Mean

Positive results suggest your body has produced antibodies against the flu virus, which could mean you’ve had the vaccine or natural infection. Negative results indicate no detectable antibodies, meaning your immune system may not have responded or you haven’t been exposed.

Common Reasons for Testing

This test is often used to verify vaccination effectiveness, especially in people with weakened immune systems. It may also be part of research studies or public health surveillance for flu monitoring.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: This test helps identify whether a person’s immune system has mounted a response to flu vaccination or infection, guiding decisions about booster doses, isolation, or preventive measures in high-risk populations.

Short name

Influenza Antibody Test

Frequently asked questions

Why might I need this test if I’ve already had the flu vaccine?
Your body’s immune response can vary. Some people may not develop detectable antibodies after vaccination, or their levels may drop over time. This test helps assess if your immune system is effectively protecting you.
What does it mean if I test negative for influenza antibodies?
A negative result means your body hasn’t produced detectable antibodies against the flu virus. This could mean you haven’t been exposed or vaccinated recently, or your immune system may not have responded as expected. Follow-up vaccination or other preventive measures may be recommended.
Can this test be used to confirm if I had the flu?
This test primarily screens for antibodies, which indicate past exposure or vaccination—not active infection. For diagnosing current flu symptoms, your doctor may recommend additional tests like rapid antigen tests or viral cultures.
  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