Most tests to determine if somebody has already been infected with COVID-19 check for antibodies, but a new study in Italy found that those tests are much less accurate than a new type that looks for a type of immune cell called a T cell.
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The people with hidden immunity against Covid-19
In short, though antibodies have proved invaluable for tracking the spread of the pandemic, they might not have the leading role in immunity that we once thought. If we are going to acquire long-term protection, it looks increasingly like it might have to come from somewhere else.