Researchers will try to deliberately infect healthy volunteers with SARS-CoV-2 (color) to test vaccines.
National Institute of Allergy and Infectious Diseases
By Jon Cohen
Science‘COVID-19 reporting is supported by the Heising-Simons Foundation.
An ethics council overseeing clinical trials in the UK today said a research team there could deliberately start infecting volunteers with the virus that causes COVID-19, a world-first experiment to investigate vaccines against to accelerate the disease.
The much-discussed ‘human challenge’ experiment will, as a first step, determine the lowest level of the pandemic coronavirus, SARS-CoV-2, needed to infect the healthy, young volunteers. The researchers plan to vaccinate additional volunteers and expose them to the ‘challenge dose’ to determine the protection and immune responses associated with it.
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The human challenge model, long used for influenza and various other infectious diseases, allows quick comparisons of different vaccines and provides a simpler way to determine why it works or not, than the large-scale efficacy trials. However, the inevitable risk of COVID-19 challenge trials is that the disease can be fatal, even to healthy young people, and there is no proven “rescue”, a treatment that reliably stops a SARS-CoV-2 infection. his tracks. Opponents also note that even a mild SARS-CoV-2 infection can have long-term consequences, saying that the questions that address human challenges can also be answered through conventional vaccination trials.
Nevertheless, many people in the UK and elsewhere have stated their willingness to participate in such studies. And scientists have said that despite the success of several COVID-19 vaccines in recent months, the trials could provide important information.
The British team, which was given permission to continue today, will select 90 healthy volunteers between the ages of 18 and 30 and, after being exposed to different amounts of SARS-CoV-2, will isolate and monitor them 24 hours a day. People who become infected will be offered rapid inhibition, a drug that has been approved in several countries for the treatment of infected people at high risk for severe COVID-19 or who has already been admitted to hospital, says the investigating officer of the trial, the immunologist Christopher Chiu of Imperial. College London. “We will take viral load measurements twice a day so that we can quite possibly see if remdesivir has a very early preventative treatment.”
Remdesivir has only been tested in hospitalized patients with mixed results, but its discoverers have long claimed that it will work better if given earlier in humans in an infection. Even if remdesivir disease occurs in these volunteers, it is probably not practical on a large scale to give the drug to newly infected people because it has to be administered, it is relatively expensive and most people have mild symptoms or not at all without treatment. not.
Human challenge trials can be used to investigate vaccines that have been adapted to be more effective against recently developed SARS-CoV-2 variants, which more easily transmit, evade the immune response or do both. But the first UK study uses an isolate of the virus obtained in the summer of 2020, before most new strains emerge. “We are currently considering which variants we should follow next, so that it is the most important for testing redesigned vaccines,” says Chiu.