Volunteers have been exposed to the coronavirus by covid-19 as part of a clinical study.
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Deliberately exposing other people to the coronavirus that causes covid-19 as part of a so-called risk study helped us understand why some people seem immune to infection.
In the first study of its kind on covid-19, conducted in 2021, a group of foreign researchers evaluated 16 other people with no known health conditions who had not tested positive for the SARS-CoV-2 virus or been vaccinated against it.
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