Many people have some immune protection against covid-19 through vaccination, infection, or a combination of both. Most recently, experts in Austria estimated the covid immunity rate in Austria at 70 percent in early August. But how much protection does each individual have?
Researchers from the Massachusetts Institute of Technology have now developed an easy-to-use test to answer that question. Their test, which works in the same way as most rapid antigen tests for Covid-19, measures the level of neutralizing antibodies that target the SARS-CoV-2 virus in a blood sample. The only difference is that the model requires one drop of blood this time.
The researchers say that easy access to this type of test could help people determine what precautions they should take against covid infection, such as whether an additional booster shot is needed. They have filed a patent for the technology and hope to work with a diagnostic company that could manufacture the devices and seeks FDA approval.
Here’s how the test works
A test cassette contains the paper test strip and a finger prick lancet to collect a small blood sample of fewer than ten microliters. This sample is then mixed with the reagents needed for the test. After about 10 minutes, the results are displayed.
To determine immunity, a blood sample is mixed with a live virus to measure how many cells in the model are killed by the virus. This procedure is too dangerous in most laboratories, so the more commonly used approaches involve noninfectious modified “pseudo viral” particles or are based on a test called ELISA (enzyme-linked immunosorbent assay), which can detect antibodies that neutralize a fragment of a viral protein. Both approaches are complicated and require trained personnel.
Similar accuracy to lab tests
The researchers conducted the tests using blood samples from about 60 people infected with SARS-CoV-2 in December 2020. Another 30 people were not infected. The researchers could detect neutralizing antibodies in the samples from those individuals previously infected with the virus with similar accuracy to existing laboratory tests. They also tested 30 serial samples from two individuals before they received the mRNA Covid 19 vaccine and at several time points after vaccination. Levels of neutralizing antibodies in the vaccinated individuals peaked about seven weeks after the first dose and then slowly declined.
The researchers now hope to work with a diagnostic company that could manufacture large quantities of the tests and obtains FDA approval for their use.
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