An international team of researchers has developed a new blood test that can help determine if a person is immune to COVID-19. The researchers, led by Ernesto Guccione, a professor of oncological sciences at New York City's Tisch Cancer Institute at Mount Sinai, developed a novel way to look for immunity by analyzing the T cells in a person's blood.

While T-cell testing already exists, the only approved test for COVID-19 takes over a week to provide results. To make the new test more accessible, the researchers worked on a way to use polymerase chain reaction (PCR) technology, which is already used to identify COVID-19.

The researchers exposed the blood sample to material from the coronavirus, hoping to elicit an immune response. If the person had immunity from COVID-19, the T cells would react to the coronavirus and create a substance that could be detected by the PCR test.

The researchers said the test results could be turned around in less than 24 hours.

Guccione said the new tests are helpful because antibody tests only tell part of the story. While antibodies tend to wane several months after an infection or vaccination, T cells tend to provide protection for up to a year.

"We know that vulnerable populations don't always mount an antibody response, so measuring T cell activation is critical to assess the full extent of a person's immunity. Additionally, the emergence of SARS-CoV-2 variants like Omicron, which evade most of the neutralizing ability of antibodies, points to the need for assays that can measure T cells, which are more effective against emerging variants of concern," Guccione said in a statement.

Health authorities in Europe have authorized the new test, but it is not yet available in the United States. The Food and Drug Administration is reviewing the technology but has not said when it expects to make a decision on granting an emergency use authorization.

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