The research paper is published on the Nature journal and service collection website Screenshot
Recently, a preprint paper published on the shared platform Research Square announced the results of the world's first "COVID-19 Human Challenge Trial".
In this study, through volunteers actively infecting the new crown virus, the research team explored the process, transmission, and immune response of the virus infection. The study found that infected people can detect the virus within 2 days, and the viral load peaks after about 5 days. 89% of infected healthy young people develop symptoms, both mild to moderate.
Back in February 2021, the study was controversial worldwide over its ethical issues after it was approved in the UK. The paper said that this data supports the safety of the COVID-19 Human Challenge trial. The research team will carry out more similar experiments in the future.
The paper's publication page on research Square suggests that the Nature Portfolio Journal is considering this preprint and has not yet been peer-reviewed.
Flowchart of test participant screening and evaluation Source: Thesis
The incubation period may be shorter, and some infected people detoxify for up to 12 days
According to the paper, 34 young volunteers aged 18 to 29 who had not been infected with COVID-19 and had not been vaccinated were involved in the trial. The team "inoculated" the volunteers with a lower dose of the new crown wild-type strain through intranasal drops.
Christopher Chiu, the study's lead researcher, said, "People in this age group are considered the main drivers of the outbreak, According to Reuters. These studies of mild infections allow for a detailed investigation of the factors that affect infection and the spread of the outbreak. ”
In the end, 18 of the 34 vaccinators were confirmed to be infected with COVID-19 by PCR testing, accounting for 53%. About 89 percent of those infected developed symptoms, all mild to moderate, of 16, and symptoms were most common in the upper respiratory tract, including nasal congestion, rhinitis, sneezing, and sore throat. 12 infected people developed some degree of olfactory impairment, and 180 days after infection, 5 still reported abnormal olfactory senses.
The study detailed and analysed the timeline of the onset and progression of infection, and provided evidence to support or refute the cognitive view of the previous process of COVID-19 infection.
The study found that in infected subjects, pharyngeal samples can detect the virus 40 hours (about 1.67 days) after "inoculation" and nasal samples can be detected 58 hours (about 2.4 days) after "inoculation". This means that the incubation period for COVID-19 is shorter than the current estimate of an average of 5 days.
After detection of the virus, the viral load in pharyngeal samples peaked at 112 hours (about 4.7 days) after infection and in nasal samples at 148 hours (about 6.2 days). Also, at peak, the viral load in nasal samples was significantly higher than in pharyngeal samples. Researchers believe that this result shows the importance of wearing a mask to cover the nose and mouth to reduce the spread of the epidemic.
In addition, the average cycle from "inoculation" of the strain to the removal of live viruses by infected people is about 10.2 days in the nose, about 8.7 days in the pharynx, and up to 12 days for some infected people to detoxify. This indicates that the current general time requirement for the quarantine period is in line with the contagious cycle of the infected person.
Comparison of time changes in viral load in nasal and pharyngeal samples
The human challenge trial was previously controversial, and the paper said the safety of the test was proven
The results support the safety of human challenge trial models, the paper said. The trial did not have serious unintended consequences, so the further development and application of human challenge trials should be supported.
According to Reuters, the research team said they currently plan to conduct a similar trial using the Delta strain by the end of 2022 and will share their research framework globally to advance similar studies.
Looking back at the process of advancing this research, there is constant controversy about the necessity and ethics of human challenge experimentation.
In February 2021, the UK Clinical Trial Ethics Agency approved the above-mentioned COVID-19 human challenge study for the first time, which was carried out by the UK Government Vaccine Working Group, Imperial College London, the Royal Free National Health Service Foundation london and hVIVO. The UK also became the first country in the world to conduct a human challenge trial of COVID-19, with £33.6 million in investment support for the study.
Just two months after the first human challenge study was approved, the UK launched another human challenge trial to expose participants who had already been infected with COVID-19 to the new crown to monitor their immune response to see if they would be re-infected. Helen McShane, a vaccinologist at the University of Oxford and lead researcher of the study, said, "This allows us to design better vaccines and treatments and understand whether people are immunoprotected after covid-19 and how long they last." ”
Charles Weijer, a bioethicist at the University of Western Ontario in Canada and a member of the WHO Working Group on Guidance on the Human Challenge Experiment on the New Coronavirus and a member of the WHO's New Coronavirus Human Challenge Experiment, previously told The Paper that as a bioethicist, he opposes such research from the perspective of ethical basis.
Chan Chi-wai, director of the AIDS Research Institute at the University of Hong Kong's Li Ka Shing School of Medicine, said in an interview with The Paper, "I don't fully agree with the human challenge experiment, the key is whether there is a need for such a test." ”
Peter Openshaw, a professor of experimental medicine at Imperial College London and a research member of the first HUMAN challenge trial on COVID-19, explained in an interview with The Guardian that "this is a very unique study that not only accelerates the understanding of the diseases caused by infections, but also accelerates the discovery of new therapies and vaccines." ”