Three-quarters of eligible Albertans have now received at least one dose of COVID-19 vaccine, and some are wondering whether to take an antibody test to verify they indeed have protection.
It’s an option some are exploring but doctors caution the tests are not an indicator of possible future infection and that there is still a range of reliability in commercially available tests.
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The Centers for Disease Control and Prevention in the United States said antibody testing is not currently recommended to assess for immunity to COVID-19 following vaccination.
“The clinical utility of post-vaccination testing has not been established,” reads a statement on its website.
However, Marc-André Langlois, a professor in the Faculty of Medicine at the University of Ottawa, said antibody tests make sense to a certain extent for more vulnerable persons.
“Elderly individuals, individuals that are taking immunosuppressant drugs for various reasons — these individuals tend not to make as potent antibody responses. In certain groups, it could make sense to investigate the antibody response to see what the levels are,” he said.
But Langlois notes tests, such as the ones done in his laboratory, are not yet routine and there is a range of accuracy in commercial tests.
“If someone is looking for convenience, and uses an at-home test, the sensitivity of those tests can be very variable.”
Langlois also said that antibodies are just one indicator of protection, saying memory B cells are produced after vaccination and they can make new batches of antibodies when re-exposed to the virus.
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“That’s how the immune memory works. Regardless of having the antibodies wane over time, we still have cells that remember how to make antibodies against this pathogen,” Langlois said.
And he is clear that a positive test is not a crystal ball into the future and does not mean a person should stop following public health measures.
“It does not mean you cannot transmit the virus to other individuals that might be vulnerable,” Langlois said.
Molecular biologist and virologist Dr. Christopher Richardson at Dalhousie University concurs, saying that the presence of antibodies does not mean a person is completely protected.
“I think we have to be very careful at realizing that just because we’re vaccinated, doesn’t mean we’re not going to get infected and spread the virus,” he said.
“The good thing about the vaccine is it’s going to reduce the symptoms no matter what, even for people that are immunosuppressed won’t get serious disease, at least there will be some protection.”
Health Canada has authorized 22 serological testing devices, but it said serological test results should be interpreted with caution.
“The performance of authorized COVID-19 testing devices has not been assessed in people who are vaccinated against COVID-19. Tests that identify antibodies to the spike protein of the SARS-CoV-2 virus will be unable to distinguish between people who have been infected and those who are vaccinated,” the Health Canada website reads.
Dr. Lynora Saxinger, an infectious disease specialist at the University of Alberta, is more critical of antibody tests. She said people should not be taking one unless they “like just spending money on things that don’t tell you anything.”
“There’s a lot of tests that are commercially available that are not high-quality tests, that you wouldn’t really be able to trust your positive or negative results on,” she said.
Saxinger also said it still is not clear what level of antibodies are needed for someone to be protected against COVID-19.
“Even if you get a number, you wouldn’t necessarily be able to say whether that number is enough right now.”
Saxinger said this area is evolving quickly but, for now, she would not rely on an antibody test.
“I don’t think they would provide you with reassurance or else a reason to change what you’re doing at the moment, honestly,” she said.
Laurie Clement, 51, had a kidney transplant eight years ago and is currently on several immunosuppressant drugs. The Edmonton woman said the last 16 months have been “very scary.” She has predominantly stayed at home, even now that she is fully vaccinated.
Clement is interested in getting an antibody test to see what next steps she can take.
“So that I know basically, do I have protection? Am I able to live my life (and) not be as worried? Can I travel? Can I live?” she said.
Clement is eager to get back to a more normal life, saying the pandemic has made things “very stressful.” Though she is aware of issues around reliability, Clement said, for her, the risk is worth it.
“The way I think of it is, it’s more than what I have now because right now, I have no clue… It gives me an idea… whether or not I have any protection,” she said.
Alberta Health Services said most people do not need an antibody test.
“Antibody testing is mostly used to help track the virus, and the test is not commonly done in Alberta,” reads a statement on the health authority’s website.