Moscow has begun distributing the domestically developed vaccine Sputnik V via 70 clinics across the city, authorities said, marking Russia’s first mass immunization against COVID-19.

The December 5 announcement by Moscow’s coronavirus task force comes as critics say the vaccine has yet to complete the advanced studies needed to ensure its effectiveness and safety in line with established scientific protocols.

Russian authorities say the vaccine would first be made available to health workers, teachers, and social workers because they ran the highest risk of exposure to the virus.

People with certain underlying health conditions, pregnant or breastfeeding women, and those who have had a respiratory illness for the past two weeks are barred from vaccination in the initial rollout in Moscow. The age for those receiving shots is capped at 60.

Moscow Mayor Sergei Sobyanin said on December 4 that “over the first five hours, 5,000 people signed up for the jab.”

The government says the vaccine will be free to all Russian citizens and that inoculation will be voluntary. The Sputnik V vaccine is administered in two injections, with the second dose expected to be given 21 days after the first.

The Russian government gave a regulatory approval to Sputnik V in early August, but the move drew considerable criticism from experts, because at the time the vaccine only had been tested on several dozen people.

President Vladimir Putin said at the time that the early vaccine recipients included one of his daughters.

On December 2, Health Minister Mikhail Murashko said that more than 100,000 people in Russia have been given the shots.

Russia reported a record high of 28,782 new COVID-19 cases on December 5, including 7,993 in Moscow, taking the national total to 2,431,731 since the pandemic began.

Authorities confirmed 508 deaths related to COVID-19 in the past 24 hours, pushing the official national death toll to 42,684.

Based on reporting by Reuters, AFP, AP