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COVID-19 antibody tests: What do they mean?

Tests give false sense of security & insecurity, infectious disease specialist says
COVID-19 antibody test
Posted at 5:00 AM, Aug 16, 2021
and last updated 2021-08-16 18:23:15-04

WEST PALM BEACH, Fla. — If you've been infected with COVID-19 or got the vaccine, you likely have antibodies. But what does that really tell you?

MORE: What's the difference between COVID-19 antibodies and monoclonal antibodies?

Waking up every day in a pandemic for Leigh Ann David means being proactive to keep her family healthy.

"Every choice we made was weighing on the options of what is our best [move] right now for our safety," said Leigh Ann, a mother of a 12-year-old and 8-year-old.

Before vaccines were available, she and her husband and two sons got tested for COVID-19 frequently and for antibodies.

Leigh Ann David, tested positive for COVID-19 after being fully vaccinated
Leigh Ann David tested positive for COVID-19 despite being fully vaccinated.

"We were just always kind of curious if we were one of those, but each time it came back that no one in my family had the antibodies," Leigh Ann said.

Leigh Ann got the COVID-19 vaccine in March and the result of her next antibodies test came back positive.

"It gave me a little bit of comfort to know that there was hope out there," she said.

But Dr. Larry Bush, an infectious disease specialist and the principal investigator for the two-dose Johnson & Johnson and AstraZeneca vaccine trials, said it's a false hope.

"My concern is that false sense of security or false sense of insecurity," Bush said.

The lab results for antibody tests state it is unknown how long antibodies last and if the presence of antibodies means immunity. In Leigh Ann's case, it didn't.

"I could feel it, feel my breathing getting shallow, so everything that happened, happened so quickly," Leigh Ann said.

COVID-19 antibody rapid test

She tested positive for COVID-19 in June, about three months after becoming fully vaccinated.

Even though she had a breakthrough infection, she feels what the vaccine did do was prevent her from having to be hospitalized.

"I am fully confident that that vaccine saved my life because I don't want to know what it would have been like for me had I not been vaccinated," she said.

But what if the antibody test shows you have none? Does that mean you have no protection? Dr. Bush said, not exactly.

"There are other parts of your immune system that are primed from the vaccine that they are not measuring," Bush said. "The last part of that is you have what's called memory cells, and even though they may be so-called sleeping, if an invader comes in, they will wake up and make antibodies."

Then, there are antibodies from natural infection, which Bush said are believed to provide better protection from future infection.

"When you've had natural infection, you produce antibodies to various parts of the virus, not just the spiked protein, plus you produce your other parts of your immune system that we call T-cells," Bush added.

The concern is no one knows how long those antibodies last either and people are being re-infected with COVID-19.

Dr. Larry Bush, infectious disease specialist in Wellington
Dr. Larry Bush discusses what we should glean from antibody test results.

"There are also studies showing that the infected people, people who have already had COVID-19, who got a vaccine booster produced a higher level of antibodies and they got re-infected less often, meaning that boosting was protective," Bush said.

Bush said he's seeing more patients asking for antibody tests, which just like the vaccine, is not FDA approved, but has emergency use authorization. He also said many at-home kits may not be credible because they have not been studied by the FDA.

"I don't recommend people go get antibody tests. I recommend that you get vaccinated," he said.

But curious and seeking confidence, Leigh Ann said she's likely to keep testing for antibodies to watch her levels over time.

"I'm technically double anti-bodied up. I'm still being cautious. I'm still wearing a mask. We're still social distancing," she said.

With her 8-year-old's only defense right now being a mask, Leigh Ann said if a third booster shot is recommended at some point, she'll get it too.

Facebook Q&A: COVID-19 antibody tests

"I am going to continue to do what I did from the start and that's make the best decision that will allow my family the greatest chance of being safe," added Leigh Ann.

Bush also explains that we are seeing recommendations for a third booster shot for the immunocompromised population, because the adaptive immune system, which responds to infection and creates antibodies to fight the virus, isn't responding the same as the general population.

"There's one other very important thing people don't understand that I think, or just don't pay attention to, in that, in the vaccine trials, for instance, the vaccine trial that I am the principal investigator for two of them, the inclusion criteria did not allow immunocompromised people in it," Bush said. "If you were taking a medicine for psoriasis or rheumatoid arthritis or Crohn's disease or recently had cancer or you were a transplant or you had HIV that wasn't under control, or you were on high dose prednisone for skin rashes for a while, you could not be in the trial. So, the people who were in the trial aren’t really mirroring the general public."

Bush said the science of the vaccine isn't changing, but more is being added on as scientists learn more about the virus and the vaccine.

"We continue [doing] the trials for two years, so every time you come in as a participant in a trial, we are still measuring your antibodies," Bush said.

Bush adds that in the vaccine trials, it's been shown that after the first dose of the vaccine, you obtained a certain level of antibodies. After you get the second dose, your antibodies will plateau, he said.

"It starts to fall somewhere. But this far out, and remember the Pfizer trials more than a year into it now, this far out, the level of antibodies still seems to be protective," Bush said. "Countries like Israel and Great Britain, where the trials were done earlier, they are starting to see that the antibody level is falling and some of those places are recommending a booster. They are months ahead of us, and we may get there."