U.K.-based researchers have conducted a unique trial in which volunteers were intentionally exposed to minimal doses of COVID-19.

“Thirty-six healthy volunteers aged 18-29 years old were enrolled according to protocol-defined inclusion/exclusion criteria,” the authors of the study said. “Screening included assessments for known risk factors for severe COVID-19, including co-morbidities, low or high body mass index, abnormal safety blood tests, spirometry and chest radiography.”

Around 50% of the volunteers did not get infected, and a few who did were asymptomatic. The symptomatic participants experienced relatively mild symptoms, such as congestion and irritation of the throat, according to the British scientific journal Nature.

Various health experts expressed their opinions on the study.

University of New South Wales immunologist Miles Davenport believes the study brings forward “a potentially important advance in how to assess future vaccine and drug efficacy,” claiming it “opens a number of important possibilities to study immunity in a controlled environment.”

David Dowdy, an infectious disease epidemiologist at Johns Hopkins School of Public Health, called the research “a very important piece of work,” as there is no “other research that’s out there is able to track … both the symptoms and the immunology from a known time of infection.”

Other experts, such as Northwestern University bioethicist Seema Shah, have questioned the morality of the study. “In my mind, it’s still not entirely clear whether these studies are ethically justified,” she said. “I’m waiting to see what else they’ve found.”

While unrelated to the study, Dr. Emil Lesho, an infectious disease physician at Rochester Regional Health, said that intentionally getting COVID for natural immunity poses many risks.

"You don’t know if it is going to be a mild or severe infection," Lesho said.