After one year of vaccination, clinical trials continue

“It’s quite difficult to find a profile. “ Infectious disease specialist Odile Launay coordinates the Covireivac platform, for clinical trials of anti-Covid vaccines in France. And the untraceable profile is that of a person over 65 who has not yet received his booster dose and would agree to participate in a clinical trial of the vaccine developed by Sanofi. One year after the launch of the vaccine campaign in France, clinical trials are continuing. And this even if the anti-Covid vaccines have already been approved by the health authorities.

The scientific process is as long as it is precise. “After phase III that everyone is now familiar with, there is a phase IV clinical trial that nobody talks about, recalls Claude Delpuech, member of the National Consultative Ethics Committee. This pharmacovigilance phase lasts for years, to detect very hypothetical rare effects. “ This last step is most often provided by national health systems. More out of rigor than fear: in medical history, no side effects have ever been detected beyond six months after the injection of a vaccine.

On the other hand, the current epidemic context poses another problem, because it makes the protection of vaccination essential. However, volunteers who participate in clinical trials have a one in two chance of receiving a placebo instead of the vaccine. And they do not know, because the tests are conducted blind. In the case of Covid-19, those responsible for clinical trials therefore now allow participants to benefit from the vaccination.

“Ethically, as soon as we have a treatment or vaccine available, effective and safe, it is proposed, indicates Claude Delpuech. Placebo should only be used if there is no alternative. “ At Pfizer, the 44,000 volunteers over 16 years of age were thus given the opportunity to “raise the blind”, that is to say to know whether they were part of the placebo group, and if so, to to get vaccinated. “We are going to open this possibility for volunteers aged 12 to 16 at the start of 2022”, adds a spokesperson for the company.

“We must not harm those who have volunteered”, confirms François Hirsch, research director and member of the Inserm ethics committee. In the very first clinical trials of AZT, an AIDS drug, he recalls, “It would have been immoral to let patients die, when preliminary data showed that it worked, and the placebo groups were quickly stopped.” In general, this switch occurs in phase III, sometimes earlier “If there is a real loss of luck”, details the expert.

But when the placebo group disappears, to whom do we compare the vaccinated group? “To control groups, simply replies Claude Delpuech. We will then compare the new treatment to those already available, to see if it is superior. “ This notion of superiority can be assessed according to different criteria: a vaccine which protects better, or for longer, which combines other protections, does not require injections, is easier to produce, etc.

For the trial coordinated by Covireivac across eleven French hospitals, participants will thus receive a third dose, either the Pfizer vaccine or one of the two vaccines developed by Sanofi-Pasteur and GSK. The aim is to compare the induced immune response but also its duration over time. “We would like to know which one is more effective in people over 65, but the vast majority of these people have already received their booster and are therefore no longer eligible for the clinical trial”, recognizes Odile Launay.

Like age, we are now trying to compare the results of the same product in participants with certain peculiarities. Find out, for example, whether pregnant women have better or less protection, or whether people on dialysis are protected for a longer or shorter period. So many tests and each time, a puzzle both human and statistical.


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