How much protection you have against COVID-19 depends on many factors. Prior infection, vaccination and immunity all play roles on how your body defends itself against the virus. The length of time post-infection or vaccination is also part of the equation. While antibody testing provides some information, it can’t pinpoint how protected you are. Now there is a new test being evaluated that may accurately assess your immunity to COVID-19 by measuring T cell response.

According to TIME, an international group of researchers recently developed a new tool to help measure COVID-19 immunity. It’s a blood test that can measure T cells, white blood cells that work together alongside virus-fighting antibodies to mount an immune response. Their study was published in Nature Biotechnology.

Study author Ernesto Guccione, a professor of oncological sciences at theTisch Cancer Institute at Mount Sinai, says that his test is faster and less labor-intensive than the previous T-cell test, called T-Detect, that was authorized for emergency use last year by the Food and Drug Administration (FDA). He and his colleagues created a process that starts with mixing a person’s blood sample with material from the SARS-CoV-2 virus. If there are T-cells present specific to that virus, they’ll react to the viral material and produce a substance that can be detected by polymerase chain reaction (PCR) technology. That will give an approximate gauge for cellular immunity, says TIME.

The test which has been licensed to the U.K.-based biotechnology company Hyris is already being used in Europe. The FDA is reviewing the technology, so it is not yet available in the U.S.

Guccione says that measuring T cells is important to determine immunity because antibody levels tend to fall off over time, even within months of vaccination or infection. Cellular immunity can last up to a year or longer.

“Monitoring both will give us a much clearer picture and will hopefully inform our re-vaccination strategies,” he said. Using this technology would help us determine when to have boosters, especially for those who ae immunocompromised and need to assess their vulnerability to COVID-19, says NBC News.

T cells are trained to remember fragments of a virus and while they won’t stop an infection, they can prevent serious illness from COVID-19. Previous studies have found that T cells are effective in recognizing all the known variants of concern, including omicron.

“The data coming out so far is very encouraging,” said Guccione. “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.”

The researchers are focused next on clinical trials to get approval from the FDA and the European Medicines Agency. Each test is expected to cost $50 and takes 24 hours to complete. The researchers are hoping to fine tune the technology to eventually provide details on the magnitude and the duration of a person’s immunity to COVID-19.