Why “human challenge” vaccine trials for COVID-19 are morally permissible, but only if we lock down, test, and contact-trace properly

By Ben Bramble

We urgently need a vaccine for COVID-19, in order to fully end our lockdowns. The trouble is such vaccines usually take years to develop and test for efficacy and safety.

Recently, a number of bioethicists have proposed “human challenge” vaccine trials to speed up the testing process. These involve volunteers receiving a trial vaccine and then being directly exposed to the virus (in isolation, of course, so that they cannot infect others). They would speed things up because we wouldn’t have to wait months for subjects to encounter the virus in the normal course of their daily lives.

But are such trials ethical? Many people feel they are not, since they might exploit these volunteers. Bioethicists have defended these trials in a number of ways. All have appealed to the huge number of lives they would save. For example: “If the use of human challenge helped to make the vaccine available before the epidemic has completely passed, the savings in human lives could be in the thousands or conceivably millions.”

In this piece, I want to do two things. First, I will challenge the claim that the payoff of such trials would be so great. They would not, I will argue, save thousands of lives. If true, this undermines the case for such trials.

Second, I will explain why such trials might be morally permissible, after all.


Would these trials really save lives?

It is wrong, I believe, to think that these trials would save thousands, let alone millions, of lives. This is because the months that would be taken off the wait for a vaccine would come at the end of this wait (say, a year from now or longer), by which time all countries will presumably have gotten considerably better at suppressing the virus and protecting their citizens. Indeed, many countries outside the US have already reduced their case numbers to near zero using a combination of lockdown, testing, and contact-tracing.

The benefit of these trials would not be thousands of lives saved, but only a bit less time in lockdown. And not only this, the sort of lockdown we’ll be enduring in a year from now will likely be one that is far more relaxed than those we are used to today, as we’ll have much experience by then of how to relax them without costing lives.

Is it really worth risking the lives of trial volunteers for a smaller benefit like this one?


Why such trials might be permissible, after all

Nonetheless, I think such trials might be permissible. Suppose that the US and UK get their acts together and start properly carrying out lockdowns, testing, and contact-tracing. In this case, in several months from now, case numbers of COVID-19 will be approaching zero. There will not be enough virus left circulating in the community for trial vaccines to be tested in the normal way at all, ever.

In this scenario, we would face a choice between staying in various forms of lockdown indefinitely, and conducting human challenge trials. Here, the benefit of such trials would no longer be, as I suggested above, a few months less of a greatly relaxed lockdown. It would instead be the avoidance of indefinite lockdown. This would be a truly massive benefit, one that might well justify the moral risks involved with allowing people to volunteer for such trials.

If we commit, then, immediately, to properly locking down, testing, and contact-tracing, then we can plan on doing morally permissible human challenge trials in several months from now, when trial vaccines are ready to test.

By contrast, if we fail to properly lockdown, test, and contact-trace, then in several months from now, there might be a sufficient amount of the virus left in our communities for human challenge trials not to be morally permissible. In this case, we might be morally required to do testing in the normal way, which could take many months longer.

The upshot? We can permissibly do human challenge vaccine trials, and get our vaccine months earlier, but only if we properly lock down, test, and contact-trace now.


Author: Ben Bramble

Affiliations:  Princeton University/Australian National University

Competing Interests: None.

Social media accounts of post author: @bramble_ben


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