A human challenge study also called a controlled human infection trial, is a type of clinical trial for a vaccine or other pharmaceutical involving the intentional exposure of the test participants to the condition tested
Human challenge studies may be ethically controversial because they involve exposing test subjects to dangers beyond those posed by potential side effects of the substance being tested.
In a new study from the Imperial College of London, researchers tested a group of 36 volunteers who completed the first human challenge study of COVID-19.
The 36 volunteers were between the ages of 18 and 30 and had no risk factors for severe COVID-19.
These people were given the virus and then monitored to examine what happened to them after infection.
The research is published in Nature Medicine and was conducted by Dr. Christopher Chiu et al.
In the study, the team infected the group with a tiny drop of fluid of the original virus strain that was delivered through a thin tube inserted in their noses.
The patients were infected in phases as a precaution, with the first 10 individuals given the antiviral drug remdesivir to reduce their chances of severe disease, which was deemed unnecessary.
They could also have been given monoclonal antibodies, but no one received them. Researchers monitored the patients 24 hours a day.
Among the 36 patients, 18 became infected. The team found two of those never developed symptoms. Those who were ill had mild cases with stuffy noses, congestion, sneezing and sore throats.
None of the patients developed lung problems, possibly because of their good health or the fact that they were given small amounts of virus.
About 83% did lose their sense of smell, at least partially. Six months after the study ended, one person has not had their sense of smell return, but it is improving.
The study volunteers shed virus for about 6.5 days, on average, or up to 12 days, even if they had no symptoms.
From the findings, the team learned a great deal about the virus. They found fact that a tiny 10-micron droplet from a cough or sneeze can make someone sick.
Other findings include that it only takes two days after a person is infected to start shedding the virus and that people shed a lot of viruses before they show symptoms.
The group will also continue studying the 18 people who didn’t get sick despite receiving the same amount of virus.
Those individuals also never developed any antibodies and were screened for closely related viruses to rule out cross-protection.
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