Coronavirus: This test claims to tell if you are well protected against COVID-19

COVID-19 immunity depends on a lot of factors including whether you have had COVID in the recent past, if you're vaccinated, whether you have any underlying health conditions and/or if you're undergoing any treatment that may be taking a toll on your immune system. However, there's still no exact way to tell whether you're well protected against the SARs-CoV-2 virus. Or is there? A group of researchers recently found a way, or rather developed a tool to estimate COVID immunity, the details of which are published in Nature Biotechnology.

While the U.S. Food and Drug Administration (FDA) is still reviewing the testing tool, it has been licensed to the U.K-based biotechnology company Hyris and is already in use in Europe.

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The study published in Nature Biotechnology describes the recent achievements of a group of researchers who developed a tool to assess COVID-19 immunity. It involves a blood test that can measure T cells - a type of lymphocyte, which is one of the important white blood cells of the immune system. These are also said to play a significant role in the adaptive immune response.

The researchers, who belong to Mount Sinai and institutions including Singapore’s Duke-NUS Medical School, were in a bid to develop a simplified technology that is widely accessible and can deliver results in less than 24 hours.

T cell, also known as T lymphocyte or white blood cell is an integral part of the immune system. They are one of the two primary types of the lymphocytes, of which B cells are the other type. B cells play a role in determining the specificity of immune response to foreign pathogens in the body. T cells on the other hand develop from stem cells in the bone marrow and help protect the body from infections and also aid in fighting cancer.

Some of the major roles of T cells include directly eliminating the infected host cells, activating other immune cells, producing cytokines and regulating immune responses.

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As far as the new research tool is concerned, scientists mix a person’s blood sample with viral protein from the SARS-CoV-2 virus. If there are any T cells specific to SARS-CoV-2 in the blood, they're expected to respond to and activate the viral material, which can then be detected via polymerase chain reaction (PCR) technology - the test type used to diagnose COVID-19.

Finally, measuring that activation, one can determine a patient’s COVID-19 immunity, as per the study.

Antibody tests do not pick up on current infection with the coronavirus. Instead they look for antibodies that are made in response to an infection, which provide immunity against the same illness in the future.

As opposed to antibody testing, which becomes less efficient within a few months after infection or vaccination, T cell testing can prove beneficial for up to a year, as per study co-author Ernesto Guccione.

He told TIME, "Monitoring both [antibodies and T cells] will give us a much clearer picture [of immunity] and will hopefully inform our re-vaccination strategies.”

Additionally, given that it is almost impossible for immunocompromised people to produce antibodies, T cell testing may work best for them, since they usually have some T cell response.

According to Guccione, widespread T-cell testing could help define those elusive "correlates of protection" by making immunity easier to study, according to the report by TIME.

“With large numbers comes clarity,” Guccione says. “That’s the hope: by using this test, we can finally get those numbers that were totally unavailable with the previous technology," he adds.

However, so far, both antibodies and T cells cannot give accurate answers to how safe a person is from COVID-19.