Russia's health officials said they were suspending the enrolment of new volunteers in its primary clinical test of the Sputnik V vaccine, The Associated Press reported Thursday quoting TASS news agency.
The decision was made after vaccine experts said enrollment of new subjects was down since the government started giving out the locally manufactured Sputnik V while the final-phase study was still being made.
Scientists at the Gamaleya Institute said it was unethical to give patients a placebo now that the vaccine was increasingly available to the public.
Russia began distributing the drug as part of a nationwide campaign early this month as phase three tests continued in Moscow.
Russia's Ministry of Health said it had already inoculated more than 31,000 participants as part of the Moscow-based clinical trial, 25% of whom were administered with placebos.
Russia has been criticized for granting Sputnik V regulatory authorization in August after the treatment had only been tried on a handful of patients. Two weeks later, the 40,000-subject test was announced.
Despite warnings by doctors to wait for the vaccine study's results, the government started giving it to patients in risk groups, like front line health workers and teachers, within weeks of approval.
Health officials accelerated the vaccination campaign this month and more than 200,000 patients have been given the shot.
The officials said that data from preliminary studies on Sputnik V's safety and effectiveness were considered as part of the decision to cut the study size. They said the study would continue and patients will be observed for six months.
The trial will now only have 31,000 subjects taking part rather than the planned 40,000, health officials said.
