What is antibody testing in the context of COVID-19?

COVID-19 antibody testing, also known as serology testing, is a blood test that's done to find out if you've had a past infection with SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19). An antibody test can't determine whether you're currently infected with the COVID-19 virus.

What does a negative COVID-19 antibody test result mean?

A negative result on a SARS-CoV-2 antibody test means antibodies to the virus were not detected in your blood.

It is unknown if all people who have a SARS-CoV-2 infection will develop antibodies in their bodies in an amount that can be detected by a SARS-CoV-2 antibody test.

Does an antibody test show if you have COVID-19?

Antibody tests should generally not be used to diagnose current infection. An antibody test may not show if you have a current infection because it can take 1 to 3 weeks after the infection for your body to make antibodies.

What does it mean to have antibodies during the COVID-19 pandemic?

When you are infected with a virus or bacteria, your immune system makes antibodies specifically to fight it. Your immune system can also safely learn to make antibodies through vaccination. Once you have antibodies to a particular disease, they provide some protection from that disease.

What does an antibody test tell you?

Antibodies are detected in the blood of people who have been previously infected with or vaccinated against a virus that causes a disease; they show the body's efforts (past infection) or preparedness (past infection or vaccination) to fight off a specific virus.

COVID-19 antibody testing explained

What is the purpose of COVID-19 antibody or serology tests?

SARS-CoV-2 antibody or serology tests look for antibodies in a blood sample to determine if an individual has had a past infection with the virus that causes COVID-19. These types of tests cannot be used to diagnose a current infection.

Can a COVID-19 antibody test tell you how much protection you might have?

Test results from currently authorized SARS-CoV-2 antibody tests should not be used to evaluate a person's level of immunity or protection from COVID-19.

Do I need the COVID-19 vaccine if I still have antibodies?

Yes, the COVID-19 vaccines are recommended, even if you had COVID-19.

How long do COVID-19 antibodies last?

At this time, it is unknown for how long antibodies persist following infection and if the presence of antibodies confers protective immunity.

How long does it take for antibodies to develop after exposure to COVID-19?

It can take days to weeks after an infection for your body to make antibodies.

Will a person with COVID-19 vaccine have a positive antibody test?

A COVID-19 vaccination may also cause a positive antibody test result for some but not all antibody tests. You should not interpret the results of your SARS-CoV-2 antibody test as an indication of a specific level of immunity or protection from SARS-CoV-2 infection.

What is a false positive COVID-19 antibody test?

Sometimes a person can test positive for SARS-CoV-2 antibodies when they do not actually have those specific antibodies. This is called a false positive.

Do people produce COVID-19 antibodies after infection?

Most people who've recovered from COVID-19 do make antibodies against the virus.

Can the COVID-19 antibody test give false negatives?

That’s because it takes a week or two after infection for your immune system to produce antibodies. The reported rate of false negatives is 20%. However, the range of false negatives is from 0% to 30%, depending on the study and when in the course of infection the test is performed.

What does a negative COVID-19 antigen test result mean in asymptomatic persons?

Negative test results using a viral test (NAAT or antigen) in asymptomatic persons with recent known or suspected exposure suggest no current evidence of infection. These results represent a snapshot of the time around specimen collection and could change if tested again in one or more days.

Does a negative COVID-19 rapid antigen test mean I don't have COVID-19?

If you have a negative test, but have symptoms of COVID-19: You may have COVID-19, but tested before the virus was detectable, or you may have another illness, such as the flu.

How long do antibodies last in people who have mild COVID-19 cases?

A UCLA study shows that in people with mild cases of COVID-19, antibodies against SARS-CoV-2 — the virus that causes the disease — drop sharply over the first three months after infection, decreasing by roughly half every 36 days. If sustained at that rate, the antibodies would disappear within about a year.

How long does it take for immunity to wane after receiving the COVID-19 vaccine?

A study published by the U.S. Centers for Disease Control and Prevention found that immunity against severe COVID-19 begins to wane four months after receiving a so-called "booster" third dose of the Pfizer or Moderna vaccines.

Can you get reinfected with COVID-19?

Reinfections can and have happened even shortly after recovery, the researchers said. And they will become increasingly common as immunity wanes and new SARS-CoV-2 variants arise.

Should I get the COVID-19 vaccine if I have recovered from COVID-19?

If I have already had COVID-19 and recovered, do I still need to get vaccinated with a COVID-19 vaccine? Yes, you should be vaccinated regardless of whether you already had COVID-19 because: Research has not yet shown how long you are protected from getting COVID-19 again after you recover from COVID-19. Vaccination helps protect you even if you’ve already had COVID-19.

Why should you get vaccinated for COVID-19 after you have already had it?

Vaccines add protection. The U.S. Centers for Disease Control and Prevention (CDC) released a report on Oct. 29, 2021, that says getting vaccinated for the coronavirus when you've already had COVID-19 significantly enhances your immune protection and further reduces your risk of reinfection.

What is the difference between the IgM and IgG antibodies tests for COVID-19?

Both SARS-CoV-2 IgM and IgG antibodies may be detected around the same time after infection. However, while IgM is most useful for determining recent infection, it usually becomes undetectable weeks to months following infection; in contrast, IgG is usually detectable for longer periods.

Do COVID-19 antibody tests detect vaccine antibodies?

• Some antibody tests will only detect antibodies from infection, not from vaccination with the virus that causes COVID-19.

Why antibody testing Is not currently recommended to assess immunity after COVID-19 vaccination?

Currently authorized SARS-CoV-2 antibody tests have not been evaluated to assess the level of protection provided by an immune response to COVID-19 vaccination. If antibody test results are interpreted incorrectly, there is a potential risk that people may take fewer precautions against SARS-CoV-2 exposure.

Does your immune system get stronger after COVID-19?

Any time you catch a virus and recover from the illness, you retain antibodies. These antibodies help your body fight off future infections so that you either don't get sick or have milder symptoms.