A newly developed blood test that measures a specific immune response in the body could help doctors gauge how much protection a person has against Covid-19, according to a new study.
The test, which focuses on the part of the immune system that confers long-term protection by prompting the body to "remember" the virus, could help make sense of the complex tangle of Covid immunity that now exists from person to person.
The test can, for instance, measure immunity regardless of whether someone has developed a level of protection from one or more natural infections or from vaccinations and booster shots. Others, who may have much lower levels of protection because they are immunocompromised, could also use the test to assess their vulnerability and see how they responded to the vaccines, said Ernesto Guccione, an associate professor of oncological sciences and pharmacological sciences at the Tisch Cancer Institute at Mount Sinai.
"Ideally, it will give you a full picture of where you stand and a comprehensive picture of your immune protection," said Guccione, one of the authors of the study published Monday in the journal Nature Biotechnology.
The researchers said they are focused next on clinical trials in order to gain approval from both the Food and Drug Administration and the European Medicines Agency.
The test involves taking a small blood sample at a clinic and mixing it with snippets of proteins from the virus. Researchers then look to see if the so-called T cells are activated in the sample.
T cells are the cornerstone of the immune system's long-term memory and typically lie in wait until they detect the presence of foreign invaders. Unlike antibody levels, which can wane following vaccinations or infections, T cells can recall a virus years, and sometimes decades, later.
Whether through vaccinations or infections, T cells are primed to "recall" fragments of a virus, including from variants that can dodge protective antibodies. This means that T cells won't stop an infection from happening, but they can prevent a patient from becoming severely ill from Covid.
Previous studies have found that T cells can recognize all the known variants of concern, including omicron, but Guccione said it's an active area of research. The scientists are continuing to refine the test and are studying how well T cells are responding against different variants.
"The data coming out so far are very encouraging," he said. "The good news is that we develop immunity against multiple proteins from the virus, and many of them do not tend to be mutated by the variants."
Tests to detect T cells have mostly been limited to labs for research purposes, and the process is usually expensive and difficult to do on a large scale, Guccione said. The new kit, however, is designed to be used widely, and results can typically be delivered in less than 24 hours, he added.
More research is needed, but he said the accuracy of the results is comparable to similar tests run in research labs.
Currently, the test can detect the activation of T cells, but the researchers are hoping that subsequent versions may be able to provide more granular detail, said Jordi Ochando, an assistant professor of oncological sciences at the Icahn School of Medicine at Mount Sinai and one of the study co-authors.
"To look at the degree of intensity of T cell immunity and have that correlated with protection — we're not at that level yet," he said. "But we hope to be at some point."
Future iterations may, for example, be able to provide details on the magnitude and the duration of a person's immunity to Covid.
Each test costs roughly $50 to run, but Ochando said it's possible that companies that license the product could include a markup on the price.
The test was developed by researchers at Mount Sinai and the Duke-NUS Medical School in Singapore. It is commercially available in Europe, as part of a licensing agreement with Hyris, a biotechnology company based in the United Kingdom.