MOSCOW (Reuters) — A majority of Russian doctors would not feel comfortable being injected with Russia’s new COVID-19 vaccine due to the lack of sufficient data about it and its super-fast approval, a survey of more than 3,000 medical professionals showed on Friday.

Russia said the world’s first vaccine against the new coronavirus will be released by the end of the month, with physicians among those who will use it on a voluntary basis. Named Sputnik V after the world’s first satellite launched by the Soviet Union in 1957, the vaccine has not yet completed its final trials and certain researchers have expressed concern that Moscow is placing national prestige above safety.

A recent survey of 3,040 doctors and health specialists, conducted by the mobile application Doctor’s Handbook and cited Friday by the RBC daily newspaper, showed that 52% of them were not ready to be vaccinated, while 24.5% said they would be willing to be vaccinated. Only a fifth were willing to recommend the vaccine to their patients, colleagues or friends.

The Russian vaccine’s approval comes before trials that would normally involve thousands of participants, commonly known as Phase III. Such trials are usually considered essential precursors for a vaccine to secure regulatory approval.

Meanwhile, Russian President Vladimir Putin has said the vaccine, developed by Moscow’s Gamaleya Institute, was safe and that it had been administered to one of his daughters. Health Minister Mikhail Murashko rejected safety concerns aired by some experts over Moscow’s rapid approval of the drug as “groundless”.