This Is the One Way to See If Your Vaccine Worked, Doctors Say
Experts say that while it's effective, only certain people should use this method.
Even beyond clinical trials, mounting research has shown that the Moderna, Pfizer, and Johnson & Johnson COVID-19 vaccines administered in the U.S. are highly effective against the virus. Further studies have even shown that the shots remain effective against the new variants that have begun to spread across different parts of the globe. So if you're fully vaccinated, you can rest assured that your shots are doing their job. But if you're in the rare position of needing to know for certain if your vaccine actually worked, doctors say the only way to find out is through a specific kind of test that's given at just the right time.
Instead of a typical rapid test, doctors say requesting a specific lab test known as an Elisa test at least two weeks after receiving the Moderna or Pfizer vaccine or four weeks after receiving the Johnson & Johnson shot can offer a better look at the spike protein antibodies generated by the doses, The New York Times reports. This is because traditional antibody tests are not designed to check for the types of markers that the vaccine has taken to your immune system.
"When most people sign up for [an antibody] test, most laboratories and providers are typically testing for anti-nucleocapsid antibodies," Luis Ostrosky, MD, an infectious disease specialist with University of Texas Physicians, explained in a blog post for the university. "The problem with that is those are not antibodies that would be created by the vaccine, but only through natural infection."
But experts still emphasize that it's very rare someone would need to know for certain about their body's response to the vaccine. "Most people shouldn't even be worrying about this," Akiko Iwasaki, PhD, an immunologist at Yale University, told The Times. "I feel a little bit hesitant to recommend everybody getting tested, because unless they really understood what the test is doing, people might get this wrong sense of not having developed any antibodies."
Still, Iwasaki said knowing whether or not your vaccination protects you can be important to immunocompromised people. She cites the example of a transplant patient whose Elisa test shows poor antibody levels using the results to convince an employer that they should be allowed to continue to work from home while offices reopen.
But even then, the results of your test may not be as conclusive as you need them to be. Quest Diagnostics, one of the manufacturers for a U.S. Food and Drug Administration (FDA)-authorized spike protein COVID antibody test, says that its test can detect antibodies from a prior infection, but post-vaccination results are not certain. "Positive results may also occur after a COVID-19 vaccination, but the clinical significance is not yet known, nor is it known how good this test is at detecting antibodies in those who have been vaccinated," the company notes on their website.
Another expert points out that antibodies alone aren't the sole determining factor in how well the immune system has been primed against the virus, such as a response in the body known as cellular immunity. "There's a lot happening under the surface that antibody tests are not directly measuring," Dorry Segev, MD, a transplant surgeon and researcher at Johns Hopkins University, told The Times.