The researchers will deliberately attempt to infect healthy volunteers with SARS-CoV-2 (color) to test vaccines.
National Institute of Allergy and Infectious Diseases
By Jon Cohen
Science‘s COVID-19 reports are supported by the Heising-Simons Foundation.
An ethics committee that oversees clinical trials in the UK said a research team could intentionally start infecting volunteers with the virus that causes COVID-19, a worldwide pioneering experiment aimed at speeding up vaccine research against the disease.
The hotly debated “human challenge” experiment will, as a first step, determine the lowest level of the pandemic coronavirus, SARS-CoV-2, needed to infect healthy young volunteers. The researchers then plan to vaccinate additional volunteers and expose them to this “challenge dose” to assess the protection and immune responses that correlate with it.
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The human challenge model, widely used for influenza and various other infectious diseases, allows for quick comparisons of different vaccines and provides a simpler way to determine why they work or fail than the large-scale efficacy tests underway. The inevitable risk of COVID-19 challenge trials, however, is that the disease can be fatal, even in healthy young people, and there is no proven “rescue” drug, a treatment that reliably stops a SARS- CoV-2 its tracks. Opponents also note that even a mild SARS-CoV-2 infection can have long-term consequences and say that the questions that human challenges address can also be answered through conventional vaccine testing.
Still, many people in the UK and elsewhere have declared their willingness to participate in such studies. And the scientists said that despite the success of several COVID-19 vaccines in the past few months, the tests can offer vital information.
The UK team that gained permission today to move on will select 90 healthy volunteers between 18 and 30 years old and, after exposing them to varying amounts of SARS-CoV-2, will isolate and monitor them 24 hours a day . People who are infected will quickly receive remdesivir, a drug approved in several countries to treat infected people who are at high risk for severe COVID-19 or who are already hospitalized with the disease, says the study’s lead investigator, immunologist Christopher Chiu, from Imperial College London. “We will take measurements of viral load twice a day so that we can see if remdesivir is effective as a very early preventive treatment.”
Remdesivir has only been tested on hospitalized patients, with mixed results, but its discoverers have long claimed that it will work best if administered to people at the start of an infection. However, even if remdesivir prevents the disease in these volunteers, administering the drug to newly infected people is unlikely to be practical on a large scale because it should be infused, it is relatively expensive and most people will experience mild or none symptoms without treatment.
Challenge tests in humans can be used to study vaccines that have been adjusted to be more effective against the recently emerged SARS-CoV-2 variants that transmit more readily, prevent the immune response, or both. But the initial study in the UK will use a virus isolate obtained in the summer of 2020, before the new strains of concern. “At the moment, we are considering which variants to look for next so that they are most relevant to the redesigned vaccine test,” said Chiu.