The first question about any vaccine is: is it safe? The second: does it work?
Recently, a large group of scientists, including 33 Nobel laureates, proposed a simple, but ethically fraught way of answering the second question: give healthy volunteers the trial vaccine, then deliberately try to infect them with coronavirus.
It’s called a “human challenge trial,” and while the logic is obvious, the ethical challenges seem equally obvious.
The practice “may seem intuitively unethical,” and there is a dark history of “unethical research involving deliberate infection of research subjects,” a World Health Organization paper published in May conceded.
“However, there is a consensus among ethicists who have reflected upon human challenge studies that the intentional infection of research participants can be ethically acceptable under certain conditions.”
The scientists’ petition argued for human challenge trials on the grounds that they would lead to a working vaccine being available much faster.
“If challenge trials can safely and effectively speed the vaccine development process, there is a formidable presumption in favor of their use, which would require a very compelling ethical justification to overcome,” they wrote.
University of Toronto epidemiologist David Fisman disagrees. He called it “unethical” in an exchange of Twitter messages.
“Why would anyone do human challenge with a virulent pathogen?”
“(There are) lots of names there that I respect but no, I don’t think that’s right. There’s a rip-roaring COVID epidemic in the U.S. There is plenty of COVID exposure happening without human experimentation with a virulent pathogen.”
Under the model proposed in the petition, the trials would have to meet a number of requirements:
- The people involved should be “relatively young and in good health,” and those with pre-existing conditions should be excluded. The petition argues that people aged 20-29 have a similar death rate from coronavirus as that suffered by living kidney donors.
- They should be given the “highest quality medical care with frequent monitoring.”
- They should be true volunteers, with children and prisoners excluded. “A large … fraction of the general population is willing to undergo meaningful risks to benefit others due to genuinely altruistic motivation,” it argues.
Oxford University’s Jenner Institute said this week that it planned to start human challenge trials for coronavirus, the kind of tests recommended in the petition, by the end of the year. It said that this approach could see testing completed in a matter of weeks.
More traditionally, a vaccine’s effectiveness would be tested on a large number of people in an area where the disease is widespread, explains the University of Toronto’s Colin Furness.
“There are a bunch of different strategies you can use to try to build immunity, or provoke immunity,” he says.
“Normally, what you do is you find a population where the disease is rampant, and you can see what proportion of the population is getting sick.”
But that approach would take too long, the petition argues:
“The rationale for human challenge trials is that they can greatly accelerate the development of a COVID-19 vaccine,” it says.
“Human challenge trials can provide information much faster than conventional efficacy trials, which take months longer.”
Furness worries that human challenge testing could happen in parts of the world where there is less accountability about medical ethics.
“Unfortunately, of course, humans have a very weak track record of ethical behaviour in medical research,” he says.
“You can speed up your testing by behaving less carefully and less ethically. So if you have a situation where you’re not worried about ethics, then you can tie people down and expose them and find out in a matter of days, rather than weeks or months, whether the vaccine is working.”
In late June, the Chinese army said it planned to test a coronavirus vaccine on soldiers. It would not say whether they were allowed to opt out of the experiment. China’s army inducts about 460,000 conscripts a year.
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