Posted on November 2, 2014 at 10:11 PM
Recently prominent bioethicists have voiced disagreement over whether it could be ethical to test experimental Ebola vaccines in placebo-controlled randomized trials. Such trials would involve taking a group of people currently infected with Ebola and randomizing half of them to an arm that receives the experimental vaccine (plus, let us assume, the best current standard of care for Ebola), and the other half of them to an arm that receives a placebo instead of the vaccine (plus the same standard of care).
The main worry with these trials is that it is unethical to give Ebola-sufferers a placebo when an experimental vaccine is available that holds the prospect of benefit. (The prospect of benefit is typically inferred from success in trials with animals; at least one experimental vaccine, ZMapp, has showed notable efficacy at preventing deadly disease in macaque monkeys inoculated with a virulent strain of Ebola.) As a prominent group of bioethicists recently pointed out, conventional care for Ebola “does not much affect clinical outcomes,” resulting in a mortality rate as high as 70%. “When conventional care means such a high probability of death,” they continue, “it is problematic to insist on randomizing patients to [a placebo arm] when the intervention arm holds out at least the possibility of benefit.” Moreover, they insist, “none of us would consent to be randomized in such circumstances.”
Perhaps many will share the sense that there is something morally problematic, perhaps even cruel, about giving Ebola-sufferers a placebo when there is a potentially beneficial vaccine available. What this line of thought misses, however, is that as of right now, experimental vaccines for Ebola are not widely available: there are many more people who could benefit from these vaccines than available doses of vaccine. In this light the mere fact that some Ebola-sufferers will receive a placebo in randomized trials seems less concerning. Unfortunately, no matter how we decide to distribute the available vaccine, some people who might benefit from it will not get it. Because of this it also seems false that no Ebola-sufferers would consent to be randomized in a placebo-controlled trial. Those who enroll in these trials will, after all, have a 1 in 2 chance of receiving the vaccine, which may be much better odds of receiving the vaccine than they would otherwise have.
The real question is how to distribute the available vaccines in the best way possible, given their limited supply. This forces us to think hard about the benefits of using the available doses of vaccine to conduct a placebo-controlled randomized trial, versus the pros and cons of other means of distribution. If placebo-controlled trials are necessary to establish the parameters and efficacy of a vaccine for Ebola, they may be of immense value in combating future outbreaks. This at least seems like one important factor to be weighed when deciding how to distribute existing doses of experimental Ebola vaccines.
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