Science

Covid-19: once a vaccine has been authorized, the ethical dilemma around placebo volunteers


If a vaccine were authorized in the United States before the end of the year, would clinical trial participants who received a placebo run into the approved vaccine? The question torments industrialists and health authorities, because their departure would complicate the long-term evaluation of vaccines.

Currently tens of thousands of people in the United States, and in other countries, have volunteered to participate in so-called phase 3 clinical trials. Usually half receive the experimental vaccine, the other half a placebo. , blindly.

The goal is to observe, over the months, how many people in each group naturally contract the coronavirus and fall ill with Covid-19. If the reduction exceeds 50% in the vaccinated group compared to the control group, then the United States Drugs Agency (FDA) could deem the vaccine to be effective and grant it what is called an emergency use authorization.

But for continued authorization, the FDA needs longer follow-up, usually six months, to confirm the safety of the vaccine, as some rare side effects may not be detected within the two months of follow-up currently scheduled for. conditional authorization.

The problem is that in general, for ethical reasons, once a drug or vaccine is approved, participants who have received the placebo in a clinical trial are informed. They could then ask for the real vaccine, or independently go for the vaccine, but in doing so, the placebo group would decrease, which would prevent a long-term comparison between the vaccinated group and the placebo group.

The risk is even greater for the dozens of projects that have not yet started their large-scale trials: who will take the risk of receiving a placebo, if a vaccine is already available in pharmacies?

The topic was discussed at a meeting of the FDA’s vaccine advisory committee Thursday, but with no real solution.

Doran Fink, of the FDA’s office of vaccines, noted that trials may continue in populations for which no vaccine has yet been approved, or for whom no doses are yet available. But for the majority, the dilemma is real.

– People ask –

“We are aware that situations could arise where it is no longer ethically allowed, and therefore no longer feasible, to continue placebo monitoring in a trial, or to start a placebo-controlled trial,” Doran Fink admitted Thursday.

“I don’t have a specific solution,” he conceded. “At this point, we asked vaccine manufacturers and other government agencies involved in the trials to think about how they might retain volunteers in clinical trials.”

One of the two companies counting on an application for conditional authorization by the end of November in the United States, Moderna (the other is Pfizer), has officially asked the authorities for instructions.

“Participants are already starting to ask when they will be able to find out whether they received the vaccine or the placebo,” said Jacqueline Miller, speaking on behalf of the company at the same meeting.

Pfizer and its German partner BioNTech, for their part, wrote in a letter to the FDA that they would have the “ethical responsibility” to inform members of the placebo group, and asked the agency to be “open” to other methods to continue to evaluate vaccines.

For now, the FDA has only one instruction: continue testing as long as it remains “feasible”.

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