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Now that tens of millions of Americans have been vaccinated against the coronavirus, many are wondering: Do I have enough antibodies to keep me safe?
For the vast majority of people, the answer is yes. That didn’t stop crowds from scrambling for the local doc-in-a-box for antibody testing. But to get a reliable answer from the test, the vaccinated people have to take a certain type of test, and at the right time.
Get the test done too soon, or rely on one that looks for the faulty antibodies—it’s very easy to do, given the confusing array of tests available now—and you might think you’re still at risk when you aren’t.
In fact, scientists prefer that the average vaccinated person not undergo antibody testing at all, on the grounds that it is unnecessary. In clinical trials, vaccines authorized in the United States elicited a strong antibody response in nearly all participants.
“Most people shouldn’t be worried about this,” said Akiko Iwasaki, an immunologist at Yale University.
But antibody tests can be crucial for people with weakened immune systems or those who take certain medications — a broad category that includes millions of people who receive organ donations, have some types of leukemia, or who take steroids or other medications that suppress the immune system. . Increasing evidence indicates that a significant proportion of these people do not produce an adequate antibody response after vaccination.
If the test has to be done, or you just want to get the test, it is essential to get the right kind of test, Dr. Iwasaki said: “I feel some hesitation in recommending everyone to get the test, because unless they really understand what the test does, People may get this false sense of not developing any antibodies.”
Early in the pandemic, many commercial tests were designed to look for antibodies to a coronavirus protein called nucleocapsid, or just N, because after infection, these antibodies were abundant in the blood.
But these antibodies are not as strong as those required to prevent infection with the virus, nor do they last as long. Importantly, N-protein antibodies are not produced by vaccines authorized in the United States; Instead, those vaccines trigger antibodies to another protein that sits on the surface of the virus, called the spike.
If people who had never been infected were vaccinated and then tested for protein N antibodies instead of spike, they could experience a rude shock.
Selfie taken by Mr. Lat during his hospital stay from Covid.Credit … David Lat
David Latt, a 46-year-old legal clerk in Manhattan, was hospitalized with Covid-19 for three weeks in March 2020, and has chronicled most of his illness and recovery on Twitter.
Over the next year, Mr. Latt was tested for antibodies several times — when he went to a pulmonologist or cardiologist for follow-up, for example, or to donate plasma. His antibody levels were high in June 2020 but steadily declined over the following months.
updated
June 20, 2021 at 1:02 p.m. ET
Mr. Latt recently recalled that the decline “did not concern me”. “I was told to expect they would naturally diminish, but I was glad I was still positive.”
Mr. Latt was fully vaccinated by March 22 this year. But the April 21 antibody test, ordered by a cardiologist, was barely positive. Mr. Latt was stunned: “I would have thought a month after the vaccination, I would have antibodies through the roof.”
Mr. Latt turned to Twitter for an explanation. Florian Kramer, an immunologist at the Icahn School of Medicine at Mount Sinai in New York, answered and asked Mr. Latt which test was used. That’s when I looked at the finer details in the test,” said Mr. Latt. He realized that it was a test for N-protein antibodies, not for elevation.
“It seems that, by default, they only give you the nuclear glove,” said Mr. Latt. “I never considered asking for another option.”
In May, the US Food and Drug Administration recommended against using antibody tests to assess immunity – a decision that drew criticism from some scientists – and provided little information about the tests for health care providers. Many doctors are still unaware of the differences between antibody tests, or the fact that the tests measure only one form of immunity to the virus.
Commonly available rapid tests provide a yes-no result and you may check for low levels of antibodies. A specific type of laboratory test, called an ELISA test, may provide a semi-quantitative estimation of spike protein antibodies.
It is also important to wait until the test for at least two weeks after the second shot of the Pfizer-BioNTech or Moderna vaccine, when antibody levels are high enough that they can be detected. For some people who receive the Johnson and Johnson vaccine, this period may be up to four weeks.
“It’s the timing, antigen, and sensitivity of the assay — these are going to be very important,” said Dr. Iwasaki.
In November, the World Health Organization set standards for antibody testing, allowing different tests to be compared. “There are a lot of good tests out there now,” Dr. Kramer said. “Little by little, all these manufacturers, all these places that you run are adapting to international units.”
Antibodies are just one aspect of immunity, noted Dr. Dore Segev, a transplant surgeon and researcher at Johns Hopkins University: “There are a lot of things going on beneath the surface that antibody tests don’t measure directly.” The body also maintains what’s called cellular immunity, a complex network of defenders that also respond to invaders.
However, for someone who is vaccinated but is immunocompromised, it can be very helpful to know that protection against the virus is not what it should be, he said. For example, a transplant patient with low levels of antibodies may be able to use the test results to convince an employer that they should continue to work remotely.
Mr. Latt did not seek another test. Just knowing that the vaccine likely gave him a new surge in antibodies, despite his test results, was enough reassurance: “I’m confident the vaccines work.”
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