COVID-19 antibody tests look for antibodies in your blood that fight the virus that causes COVID-19.
Antibodies are proteins created by your immune system that help you fight off infections, according to the U.S. Centers for Disease Control and Prevention (CDC). They are made after a person has been infected or has been vaccinated against a disease.
While a COVID-19 antibody test can be a useful tool for doctors, with more people getting vaccinated in the U.S., FiveThirtyEight founder and editor-in-chief Nate Silver recently asked on Twitter if it’s possible to tell the difference between COVID-19 antibodies and vaccine antibodies.
Is it possible to tell the difference between COVID-19 antibodies and vaccine antibodies?
Yes, it is possible to tell the difference between COVID-19 antibodies and vaccine antibodies.
WHAT WE FOUND
The CDC says on its website that antibody tests — also known as serology tests — look for antibodies in your blood that fight the virus that causes COVID-19. Antibody tests might tell you if you had a past infection and should generally not be used to diagnose a current infection.
“There are ways to distinguish antibodies that are generated from the vaccine versus antibodies that are generated from natural infection,” Dr. Amish Adalja, a senior scholar at the Johns Hopkins Center for Health Security, told VERIFY.
According to Dr. Omid Bakhtar, a board-certified pathologist at SHARP Healthcare, the COVID-19 antibody test was created in the early days of the pandemic as a way for doctors to diagnose if someone previously had the coronavirus. It looked for antibodies to the nucleocapsid protein, which only appears in those who recovered.
When the COVID-19 vaccines were created, Dr. Bakhtar says researchers wanted a way to determine if the antibodies were taking hold within a person’s immune system. Since the vaccines don’t contain SARS-CoV-2, the virus that causes the coronavirus, the nucleocapsid test would not work. Instead, the vaccines contain a spike protein, which is found on the surface of the virus that causes COVID-19. A separate antibody test was created to check for that.
“Remember, the vaccine only contains the spike protein so an antibody to the spike protein would be consistent with vaccination or natural infection, but antibodies to other parts of the virus, for example, the nucleocapsid protein, would be distinct to natural infection,” said Dr. Adalja.
According to the CDC, vaccination is a safe and effective way to teach your body to create antibodies.
“COVID-19 vaccines teach your body to produce antibodies to fight infection from the virus that causes COVID-19. If you get an antibody test after receiving a vaccine, you might test positive by some (but not all) antibody tests. This depends on which type of antibody the specific test detects,” said the CDC.
However, the CDC and the U.S. Food and Drug Administration (FDA) say antibody tests should not be used to evaluate a person’s level of immunity or protection from COVID-19 until more research is done.
“Antibody testing is not currently recommended to determine if you are immune to COVID-19 following COVID-19 vaccination,” said the CDC. “Antibody testing should also not be used to decide if someone needs to be vaccinated.”
According to the FDA, if antibody test results are interpreted incorrectly, there is a potential risk that people may take fewer precautions against COVID-19 exposure, which can increase their risk of infection and may result in the increased spread of the virus.