Washington (AFP)
In the United States and elsewhere, regulators, experts and laboratories face an ethical dilemma: when should participants in clinical trials of Covid-19 vaccines who have received a placebo be offered the real vaccine?
The question is most pressing for the vaccine from Pfizer and BioNTech, which is expected to be the first authorized in the coming days in the United States, after authorizations in the United Kingdom and other countries.
The trial has recruited since the end of July 44,000 people in several countries including the United States: half received a placebo (saline solution) and the other the vaccine, blind and randomly, which is called a trial "randomized".
All of them live their lives normally.
The usefulness of the placebo is to have a control group: the goal is to compare the number of cases of Covid-19 and the possible adverse effects between the two groups.
Resolving the dilemma requires balancing the interests of society, which are to continue the blind trial for as long as possible in order to accumulate as much data as possible, and the interests of participants, which cannot be demanded. absolute altruism and many believe they have the right to be vaccinated as a priority as soon as a vaccine is deemed safe and effective.
The Medicines Agency's (FDA) Vaccine Advisory Committee discussed the subject Thursday at a public meeting.
An expert on the matter, Steven Goodman of Stanford, has warned that participants in a trial have no absolute right to be vaccinated before it is "their turn" in the rest of the population: it is part of the contract.
He suggests that participants be informed of what they received in the arm on the day the vaccine is authorized for the category of the population to which they belong.
Placebo people could then ask to be vaccinated immediately.
This method has the advantage of encouraging participants to stay in the trial: they would thus continue to provide important data on the side effects and the effectiveness of the product.
They would not have an interest in resigning from the trial to try to get vaccinated independently.
This is what Pfizer proposed to the FDA, with a vaccine offered in all cases to all at 6 months, and follow-up for 18 months.
- Maintain confidence -
Whatever the regulator decides, the reality is that its power will be limited, because the participants are and will remain free.
Nothing will prevent a 65-year-old from going to the local pharmacy the day the vaccine is available there to his neighbors of the same age.
In addition, many participants probably already know which group they belong to: these are those who have had severe pain around the injection site in the arm.
It is known from published data that this is a common side effect of the vaccine.
In practice, participants are likely to wait "two, three or four months" maximum after authorization, according to Steven Goodman.
"There will be a time when we can no longer continue the randomized placebo trial," he said.
If we wanted to keep the blind aspect of the study, we could vaccinate the placebo group, and give a placebo to the vaccinated group, without revealing to the participants their status, he proposed.
The priority will be to maintain the confidence of the volunteers, insists the professor.
The placebo participants will therefore be vaccinated, that's for sure.
"The question is when?"
Moncef Slaoui, chief scientist of the Trump administration's Operation Warp Speed, said this week.
Even when the control (placebo) group wears off, the trial will continue to produce useful data on participants' immune response and side effects.
On the other hand, another puzzle will emerge: when one or more vaccines become available, how will the developers of the other experimental vaccines be able to recruit participants in their own clinical trials?
Who will accept the 50% risk of receiving a placebo, when a vaccine is available in pharmacies?
At this stage, the only clinical trials still possible could be on populations for which no vaccine has yet been authorized, for example young children.
© 2020 AFP