For some people, knowing if they’ve had COVID-19 is an important step to getting back to normal. If they’ve had the disease, they may have some immunity to future infections (though that’s not yet certain) and may be willing to take greater risks, such as dining out and visiting friends.
But knowing if you’ve had the disease is a challenge: More than 40 percent of people who have been diagnosed with COVID-19 had no symptoms, according to a study published in late May. And Centers for Disease Control and Prevention estimates from April suggest that up to two-thirds of people infected with the disease are undiagnosed.
That’s where COVID-19 antibody tests come in. Antibodies are an essential part of your immune system. When a pathogen, like bacteria or a virus, invades your body, antibodies bind to the invader and neutralize it, minimizing its damage. Your body came with some antibodies, which were passed from your mother. But most antibodies are developed over time when you’re exposed to pathogens.
With most viruses, once you’ve built up enough antibodies, you’re generally considered immune to reinfection – at least for a while. Again, this isn’t certain with the coronavirus. But scientists believe coronavirus antibodies may only last a few months after someone has become infected with COVID-19, according to a study published in Nature Medicine. Additionally, scientists found that people without symptoms had a weaker antibody response than those with symptoms. And within eight weeks, antibody levels in 40 percent of people without symptoms fell to undetectable levels, compared to 12.9 percent of people with symptoms. Undetectable levels of antibodies doesn’t mean your body is unable to fight a COVID-19 infection. The body may be able to successfully fight reinfection even if antibodies aren’t shown in a test.
Before getting into too much detail about antibodies, it’s important to understand some basics of the immune system. Your blood contains two main types of cells: Red cells, which carry oxygen to tissues and organs, and white cells, which are the immune cells you need to fight infections. White cells contain three types of pathogen fighters:
- Macrophages: These cells swallow up germs and dead cells. When it does this, it leaves behind antigens, parts of the invading germ. The body identifies these antigens and produces antibodies to attack them.
- B-cells: These cells produce the antibodies to attack antigens left behind by macrophages.
- T-cells: These cells attack cells in your body that have already been attacked and infected by an invader.
When you catch a virus, these three cell types work in concert to fight the infection, clean it up and leave a roadmap for future fights against the same virus.
How Vaccines Work
Vaccines take advantage of this system. Vaccine serum typically contains either weakened viruses that can’t infect you or dead viruses, both of which trigger the immune system just like a virus or bacteria would. The body develops antibodies so that it can recognize a pathogen and fight it in the future.
Coronavirus germs are like other viruses. Once your body detects the COVID-19 pathogen in your system, B-cells release an army of antibodies to disable the virus and protect you. This is why some researchers are using antibodies from recovered COVID-19 patients (also known as convalescent plasma therapy) to treat patients with COVID-19.
There are now COVID antibody tests that can detect the presence of specific antibodies, suggesting you were previously infected with COVID-19. Once you have fully recovered, you can request an antibody test. As long as you meet symptom criteria and there isn’t a shortage of tests in your area, you can visit a healthcare professional who will collect a blood sample through a venous blood draw or finger prick.
Blood draw tests identify two types of antibodies, IgM and IgG. IgM antibodies develop in the earlier phase of a COVID-19 infection, whereas IgG antibodies are usually detected after you’ve recovered, typically indicating some immunity has been developed. Blood samples are sent to a lab and can take up to seven days for results. Even though the wait might be inconvenient, these blood draws are considered more reliable than finger prick tests.
Finger prick tests (or IgM rapid tests) are only able to recognize IgM antibodies. Although results are available in 10 to 15 minutes, these tests are less accurate than blood draw tests, often producing false positives and false negatives.
Antibody tests should not be used to diagnose COVID-19. If you’ve been exposed to coronavirus germs, it can take up to three weeks for your body to develop antibodies to fight it. And antibody tests may not show the presence of an active virus like a nasal swap or throat culture can.
What should you do if you test positive?
First, don’t read too much into the results. Continue practicing precautions such as social distancing, wearing a face mask, staying home when ill and handwashing. Just because you have antibodies does not mean you are immune from catching (or spreading) the coronavirus. Researchers just don’t know yet if — or for how long — antibodies to COVID-19 will protect you.
Second, inform your primary care doctor of your results, as it will help your doctor decide what types of follow up tests and care you might need. For instance, your doctor may make your cardiovascular health more of a priority, as research has shown that patients are up to seven times more likely to have a heart attack following a viral infection. And early research into COVID-19 suggests that it doesn’t just damage the lungs — it can damage the heart.
What should you do if you test negative?
Maintain precautions. If you have COVID-19 symptoms, you may be infected but haven’t built up enough antibodies to register on a blood test.
Are you a prime candidate for testing?
Talk to your MDVIP affiliated doctor about COVID antibody tests, especially if you’ve experienced COVID-like symptoms over the last few months and/or if you:
- Are 65 or older
- Have a history of high blood sugar, i.e., an HbA1c of 6.5 or higher
- Have been diagnosed with cardiovascular disease
- Have been diagnosed with high blood pressure
- Are overweight/obese
- Have had elevated MPO levels on your last two MDVIP Wellness Program results, i.e., higher than 540 pmol/L
MDVIP has partnered with CHL/Quest Diagnostics to conduct a study across the MDVIP network on COVID-19 and its associated risk for cardiovascular events. If you have questions about COVID-19, talk to your doctor. If you don’t have a doctor, considering partnering with an MDVIP-affiliated physician. Find a physician near you and begin your partnership in health »
Tiberian MA, MPH, CHES, J. (2020, June 19). Should You Get a COVID Antibody Test? Retrieved July 08, 2020, from https://www.mdvip.com/about-mdvip/blog/should-you-get-covid-antibody-test