Europe's vaccine watchdog has launched a review of the Russian-made Sputnik V COVID-19 vaccine.
The European Medicines Agency said in a statement on Thursday that the rolling review is based on results from laboratory studies and clinical studies in adults.
"These studies indicate that Sputnik V triggers the production of antibodies and immune cells that target the SARS-CoV-2 coronavirus and may help protect against COVID-19.
"EMA will evaluate the data as they become available to decide if the benefits outweigh the risks. The rolling review will continue until enough evidence is available for formal marketing authorisation application," it added.
The announcement comes just days after Slovakia became the second European Union member state, after Hungary, to receive deliveries of the Russian-made vaccine despite it not being approved by the regulator, deepening a political crisis in the eastern European country.
The EMA has so far approved three vaccines for use across the bloc. These were developed by Pfizer/BioNTech, AstraZeneca/Oxford University, and Moderna. It is currently evaluating the jab by Johnson & Johnson and is expected to give its approval in mid-March.
Kirill Dmitriev, CEO of the Russian Direct Investment Fund, which financed the Sputnik V vaccine, said in a statement that he welcomed the EMA's rolling review and said they have given the watchdog "comprehensive data".
"Following EMA approval, we would be able to provide vaccine for 50 million Europeans starting June 2021," he added.
Data released by Sputnik V suggests the vaccine, which uses a spike protein to trigger an immune response, has a 91.6 per cent efficacy rate. The two-dose jab can be stored in a conventional refrigerator and costs under $10 per shot (€8.5).
It has been deployed in 40 countries worldwide, including European nations Serbia, Montenegro, Moldova, and Hungary. Slovakia received its first shipment of 200,000 doses over the weekend.
Hungary, which started administering it Sputnik V in mid-February, said its decision to start using the jab was spurred on by Brussels' slow coordinated roll-out. The country's health regulator approved Sputnik V in January.
Prime Minister Viktor Orban told local radio last month: "Every day that we spend waiting for Brussels, we lose a hundred Hungarian lives.
"Why should we think that European experts are smarter than us? I trust the Hungarian Public Health Centre more than the one in Brussels," he added. The country has also started using China's Sinopharm vaccine.
The EMA defended itself last month, however, saying that Sputnik V had not applied for a rolling review or marketing authorisation.