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COVID: The First Human Challenge Study Brings Valuable Insights


To infect COVID-19, you need a small droplet containing the virus (about the same width as a human blood cell).

This is just one of the discoveries from studies that deliberately infected healthy volunteers with the SARS-CoV-2 virus.The survey results are Published in Nature Medicine on Thursday..

Challenge research can be controversial as it involves deliberately giving someone a virus or other pathogen to study its effects on the human body. Even with precautions, there are risk factors, especially when studying new viruses.

However, they are also very valuable for understanding the course of infection.

“In fact, there are no other types of studies that can do that. Usually, patients only get your attention when symptoms appear, so you miss all the days before the infection.” Said the principal investigator. Dr. Christopher Chiu, an infectious disease specialist and immunologist at Imperial College London.

Volunteers were carefully selected

The study began in March 2021. The 36 volunteers were between the ages of 18 and 30. They were only allowed to participate in the absence of severe COVID-19 risk factors such as overweight and decreased kidney and liver. There is a functional or heart, lung or blood problem. They also signed an extensive informed consent form to participate.

To further minimize the risk, researchers conducted the study in stages. The first 10 infected volunteers got the antiviral drug remdesivir to reduce their chances of progressing to a serious illness. The researchers also prepared monoclonal antibodies in case someone got worse. Eventually, remdesivir turned out to be unnecessary, and researchers didn’t need to give antibodies to anyone.

Volunteers obtained a small drop of liquid containing the first virus strain detected through a long, thin tube inserted into the nose.

They stayed in a room at the Royal Free Hospital in London for two weeks, which is medically monitored 24 hours a day and has a special air flow to prevent the virus from escaping.

Half infected

A total of 18 participants were infected, two of whom had no symptoms. Among those who became ill, their illness was mild. I had a stuffy nose, a stuffy nose, sneezing, and a sore throat.

Most of the study participants (83 percent) who caught COVID-19 lost their sense of odor, at least to some extent. Nine didn’t smell at all.

This now well-known symptom has improved for most people, but six months after the end of the study, one person has not returned to normal but has improved.

This is a concern as another recent study found that this odor loss was associated with changes in the brain.

Chiu says researchers have given participants cognitive tests to check short-term memory and reaction time. They are still looking at the data, but he thinks those tests “will be really useful”.

None of the research volunteers developed lung involvement in their infection. Chiu believes this is because they are young, healthy and inoculated with a small amount of the virus.

Beyond the loss of smell, other symptoms did not persist.

Take a closer look at the infection as it travels through the body

Under these carefully controlled conditions, researchers could learn a lot about the virus and how it travels through the body:

  • A small amount of virus, about 10 microns (the amount of a drop that someone sneezes or coughs), can make someone sick.

  • The incubation period of COVID-19 is very short. It takes about two days after infection for a person to start shedding the virus.

  • People shed a large amount of virus before they show symptoms (make sure epidemiologists understand).

  • On average, young and healthy research volunteers shed the virus for six and a half days, while others shed the virus for 12 days.

  • Infected people can shed high levels of the virus without any symptoms.

  • Approximately 40 hours after the virus was introduced, it was detected in the back of the throat.

  • It took about 58 hours for the virus to appear from the nose to the swabs, eventually growing to much higher levels.

  • Rapid at-home immunochromatography is very effective in detecting when a person is infected. The study found that these types of tests can diagnose infection before 70% to 80% of viable viruses are produced.

Chiu says his study emphasizes much of what we already know about COVID-19 infection. That’s why it’s so important to cover both your mouth and nose when you’re sick, especially to protect others.

More research projects planned

This challenge study was so successful that Chiu plans to do it again. This time around, we are targeting people vaccinated with the Delta variant to study the immune response.

He says his team also plans to continue studying people who didn’t get sick.

“That’s really interesting,” he said. About half of the study participants did not get sick or develop antibodies, even though they took the exact same dose of virus.

Everyone was screened for antibodies to closely related viruses, such as the original SARS virus. Therefore, it was not mutual protection to keep them safe. It was something else.

“There are many other things that can help protect us,” Chiu said. “There is a barrier in the nose. There are various types of proteins and stuff that are very old and primitive protection systems, which may contribute to being uninfected. We understand. What are they really interested in trying? “

Understanding what other factors are working can help provide more general protection to people in the event of a future pandemic.

Dr. Catherine Edwards, a pediatric infectious disease specialist at Vanderbilt University and author of an editorial published in parallel with the study, said the study provides important information on SARS-CoV-2 virus infection and transmission. rice field.

Blood and tissue samples collected for the study will continue to be analyzed for the next few years, she said. “I think they’re all in the freezer and dissected, so I think it should be very powerful.”

In the end, she believes that this study has rested a lot of fear of human challenge studies and paved the way for others.

“We don’t do challenge studies on babies, and even 75-year-olds with chronic lung disease don’t do it,” she said. But for young and healthy people, “I think these are useful studies.”




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