Moscow's Gamaleya Institute, developer of the first Russian vaccine against COVID-19, said on Wednesday it would no longer give placebos to volunteers in its large-scale final-stage trials for the Sputnik V shot, RIA news agency reported.
Alexander Gintsburg, the institute's director, said the Health Ministry had authorised the move. "Everything there has been proven and the pandemic is ongoing, so a placebo is not good at all," he was quoted as saying.
Gamaleya's experience underscores problems for drugmakers around the world as the pressure of the coronavirus pushes regulators to authorise new vaccines and start administering them faster than they normally would.
Russia is also in a unique position because it approved Sputnik V very early, in August, after stage I and II human trials showed that it was safe and produced the antibodies needed for a protective immune response.
More than 200,000 people have now been vaccinated in a national rollout. As a result, volunteers in the final, stage III trial, which began in September, have begun quitting to try to get the vaccination.
In stage III, the gold standard, a large number of volunteers randomly receive either the vaccine or a control injection of placebo, without knowing which they have been given, and their infection rates are compared after a sufficient number have become infected through natural exposure.
If the trial is shrunk or shortened, this reduces the chances that it will pick up any unexpected effects of the drug.
But with mass vaccinations under way - and the latest stage III results showing 91.4% effectiveness - participants say it is wrong to shut them out now.
Pfizer Inc of the U.S. and Germany's BioNTech SE, whose vaccine is being rolled out in Europe and the United States, say they plan to notify stage III trial participants in the U.S. once they become eligible to receive shots.
These participants could then opt to be "unblinded" by being told whether or not they received a placebo.
The American drug maker Moderna proposed last week to unblind all its trial volunteers at the same time, offering the vaccine to those who had received a placebo.
In Moscow, two trial volunteers, married couple Alex and Olga said they had spent around $200 each on several antibody tests, widely available in private clinics, and found no immune response.
Concluding that they had probably received the placebo, they quit the trial, hoping to get a vaccination.
Igor said he had thought his participation was anonymous, and was now dismayed to find that his name was on a list of people barred from receiving the inoculation, while others could get it.
"I'll be looking for ways to get vaccinated!" he said.
Six volunteers told Reuters they had left the trial in this way and had, despite the administrative obstacles, found ways to get vaccinations, some by travelling outside the capital.
Around 20 others said on social media that they had left the trial, but declined to share details. All asked for their surnames not to be made public.
Of 40,000 participants who were sought, around 30,000 have so far been recruited and received an injection - a quarter with the placebo.
The health ministry did not respond to a request for comment on how many people have formally left the trial.
Gamaleya's interim stage III results were based on 78 confirmed infections, 62 of them in the placebo group.
Gamaleya's Gintsburg said he would like to identify those who had already received a placebo and offer them the vaccination, "but it's still unclear whether the regulator will allow this".