Theel pointed to a recent study of breakthrough infections among 1497 fully vaccinated health care workers in Israel. Still, she wrote, “it’s not a simple relationship-there is no clear titer at which you can say whether a particular person is protected.” What’s more, different neutralizing antibody thresholds, or even different immune responses altogether, may correlate with protection against asymptomatic, symptomatic, or severe disease. In an email, Nicole Doria-Rose, PhD, a staff scientist and chief of the Humoral Immunology Core at the National Institutes of Health’s Vaccine Research Center, noted that antibodies that bind to the SARS-CoV-2 spike protein-particularly neutralizing antibodies-“do correlate with protection.” For example, higher titers were associated with increased protection in 2 phase 3 studies: one not yet peer-reviewed of the mRNA-1273 ( Moderna) vaccine and another of the ChAdOx1 nCoV-19 ( Oxford/AstraZeneca) vaccine. It’s also that the protective antibodies and their thresholds still haven’t been fully worked out. The problem isn’t simply that the tests weren’t designed to assess immunity, experts told JAMA. Therefore, the agency in its May 19 communication stated that “results from currently authorized SARS-CoV-2 antibody tests should not be used to evaluate a person’s level of immunity or protection from COVID-19 at any time, and especially after the person received a COVID-19 vaccination.” Depending on the assay, people who weren’t previously infected could test negative for antibodies despite having vaccine-induced immunity. ![]() Plus, the FDA cautioned that some tests detect antibodies the immune system likely produces only after natural infection with the virus. Their ability to predict protection against the virus based on those antibodies hasn’t been proven. The SARS-CoV-2 serology tests that eventually received FDA Emergency Use Authorization (EUA) have demonstrated high sensitivity and specificity, but that accuracy is for detecting antibodies. “I am aware of individuals getting tested just to see if they’ve ‘reacted’ to the vaccine or if they have ‘immunity,’ despite our best efforts to educate,” she wrote in an email. And Florida-based Epitome Risk Solutions promises that the direct-to-consumer SARS-CoV-2 serology assay it sells for $170 “correctly identifies the number of neutralizing antibodies you have with 100% specificity” so that in “24-48 hours you’ll know if your immune system is still protecting you from COVID” after vaccination or infection.Įlitza Theel, PhD, director of the Mayo Clinic’s Infectious Diseases Serology Laboratory, confirmed the worrisome trend. A recent New York Times article described concierge clinicians who regularly test their clients for SARS-CoV-2 antibodies. A spokesperson for the agency reiterated the position in an email to JAMA in September. No, says the US Food and Drug Administration (FDA), which discouraged antibody testing as a do-it-yourself immunity check in a communication to the public and clinicians this past spring. Could a simple blood test reveal whether the vaccine was working or, later, if it was time for a booster shot? But for some, the arrival of COVID-19 vaccines revived their interest in serology. Which specific antibodies guarded against SARS-CoV-2 reinfection? How high did their levels need to be? And how long would they provide a reliable defense?Īs the assays’ usefulness for individual patients became less clear and testing for active infections expanded, the public’s clamor for antibody testing waned. More fundamentally, the so-called correlates of protection were unknown. The early consumer tests’ accuracy was unproven, making the results somewhat dubious. Shared Decision Making and Communicationīut as the pandemic unfolded, the concept of an immunity passport based on having antibodies didn’t pan out. ![]() Scientific Discovery and the Future of Medicine.Health Care Economics, Insurance, Payment.Clinical Implications of Basic Neuroscience.Challenges in Clinical Electrocardiography.
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