In a few weeks, dozens of young and healthy volunteers in the UK will be intentionally exposed to coronavirus as part of the world’s first COVID-19 human challenge trial.
The project, which received ethical approval on 17 February from the UK government, will study the amount of virus needed to start an infection. Finally, researchers could address other issues, such as how different vaccines work.
In human challenge tests, volunteers are deliberately infected with a pathogen in a controlled environment. Researchers can then closely study disease progression or possible treatments with a level of detail not very available in traditional trials, which require waiting for participants to catch the disease on their own.
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The possibility of COVID-19 challenge testing has sparked controversy; some question the ethics of putting volunteers at risk for a relatively new pathogen whose long-term consequences are not fully understood (SN: 27/05/20). For this trial, the promise of accelerated research outweighs the risks to participants, UK regulators say.
“I think there could be a case where the risks are acceptable for young, healthy volunteers,” says Seema Shah, a bioethicist at Northwestern University Medical School in Chicago who is not involved in the trial. "People may still disagree," he adds, "especially with the uncertainty about long-term morbidity."
Within a month, researchers hope to enroll up to 90 healthy volunteers between the ages of 18 and 30 who have not contracted the coronavirus. People under the age of 30 have a lower overall risk of hospitalization or death than the elderly, but serious illness can still occur (SN: 9/9/20).
In isolated hospital wards, volunteers will be exposed to different levels of an original variant of coronavirus circulating since March 2020. Volunteers will be monitored throughout the day, allowing researchers to determine the minimum dose of coronavirus needed to start the infection, Andrew Catchpole, scientific director of hVIVO, a pharmaceutical services clinical research organization in London that will help conduct the trial, said in a press release. Finding out the amount of exposure that leads to infection is one of the long-open questions about the COVID-19 pandemic. Researchers can also track a volunteer’s immune response throughout the infection.
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The answers to these basic research questions lay the groundwork for future studies. For example, knowing the minimum infectious dose could allow for future tests, yet to be approved, that try to test vaccine candidates or determine whether new variants of the virus can dodge naturally acquired immunity.
Those questions are important to answer, Shah says, but with coronavirus variants that are more contagious and perhaps more deadly, now becoming dominant, the question arises of the impact this trial may have (SN: 15/1/21). They may behave differently from the strain used in this trial, weakening the broader applicability of their results.
For example, a future trial that makes comparisons of vaccine candidates may be valuable, but, Shah asks, “if you’re doing a challenge trial with a strain that is ultimately no longer the dominant strain, who does that tell you about the effectiveness of the vaccine? vaccine? "
Exactly how this recently approved human challenge will work remains unclear, as details have not been made public. The researchers say they plan to publish the protocol and an explanation of the study design at some point in the future.
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