What do we know about COVID-19 immunity?

Social distancing, isolation, face coverings, business closures and constant hand washing is our new normal. It may seem like you’re living in a world turned upside down by COVID-19. These behavioral changes are the best tools we have for now - until we can rely on our body’s natural defense system. Identifying, testing and creating immunity in your body is how we will win the fight against COVID-19, but they all require one thing: time. Thankfully, there is promising work being done to identify COVID-19 immunity.

How long will COVID-19 immunity last?

Our immune system responds to the exposure of viruses and bacteria by creating antibodies. You may remember from high school biology that these antibodies are elements in your blood that fight infection and illness. How the body creates immunity and how we test people for it is a critical step in the fight against new diseases. But how long immunity lasts varies depending on the virus.

Dr. Ruth Berggren, an infectious disease specialist at University Health, has been monitoring research on the topic of immunity to COVID-19. “We know people develop antibodies to the SARS-CoV-2 virus that causes the disease called COVID-19. We have also learned that recovered COVID-19 patients have antibodies against SARS-CoV2 in their blood for at least two weeks after they recover,” Dr. Berggren said.

“What we do not know is how protective these naturally developed antibodies are against COVID-19. Will they stick around long enough to prevent from future infection or clinical illness? If they are protective, how long will they last? The ideal scenario to wish for would be like chicken pox: once you get it, you develop life-long protective immunity.”

Dr. Berggren says the virus that causes COVID-19 can be more closely compared to the virus that caused the SARS outbreak in 2003. “Think of the SARS virus as a cousin of SARS-CoV-2; they share a lot of similar genetic material and belong to the same family of coronaviruses. Antibody testing shows SARS-CoV immunity peaks at around four months and offers protection for roughly two to three years. That is hopeful news, because if true for SARS-CoV-2, it suggests that once recovered from COVID-19, a person could be protected long enough for there to be an effective vaccine available,” Dr. Berggren explains.

But Dr. Berggren warns we can’t rely too heavily on what we know about our body’s response to other coronaviruses. “Different coronaviruses affect the body in a variety of ways to produce distinct illnesses, from mild common colds to severe pneumonia, to life-threatening adult respiratory distress syndrome,” she says. “Although antibodies that protect from SARS last 2-3 years, immune protection against infection with other human coronaviruses, such as those which cause common colds, is short-lived.”

How do we test immunity levels?

Serology testing is a type of blood test that checks for the presence of antibodies in your blood. Antibodies are all different—created to fight a specific virus or bacteria. So serology tests can identify if your body has created the antibodies for a particular virus. Your body starts creating antibodies as soon as you get sick, but it can take anywhere from 7-14 days after you recover for those antibodies to be recognized in a serology test.

Antibody tests for SARS-CoV-2 were described in medical literature as early as April 2020, says Dr. Berggren. “What takes a lot longer is knowing what the antibody tests mean. We don’t know how high the SARS-CoV-2 antibody level has to be to protect you or how long the antibodies will last.”

Testing for COVID-19 antibodies

It’s important for researchers developing tools like serology testing for COVID-19 to have reliable data that shows the tests are identifying the right virus. We also need more information about how our bodies are actually fighting COVID-19 to know if those antibodies can protect us enough to begin lifting social distancing restrictions.

All of these things take time. And the only way to know if the process is working is with a lot of scientific research data to back up the findings.

Dr. Berggren does have a recommendation for how to gather this data about COVID-19 immunity. “It would be ideal to test people with a nasal swab that detects virus genetic information and an additional antibody test on their blood. We would then follow up on them and draw their blood again in about 2-3 weeks. If there was detectable virus genetic information, indicating the presence of the virus itself, ‘how long did it take to develop antibodies and how high were their levels?’” she asks. “Then check them again at future time intervals, interview them to learn if they were exposed again, and learn whether subsequent exposures made them sick or not.”

“Such studies will take a lot of time,” says Dr. Berggren, “but the effort will pay off if we ultimately have an antibody test that tells us whether or not it is safe for a health care worker to go back to work.”

Dr. Tyler Curiel, Professor of Medicine, Immunology & Molecular Genetics at UT Health San Antonio also contributed to facts for this blog.

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