President Vladimir Putin said Tuesday he expected the Russian-made Sputnik V jab to protect him as he started to self-isolate after coronavirus cases were detected in his inner circle.
Putin said it will be a "natural experiment" as Russia struggles with stubbornly high coronavirus infection rates and a vaccine-sceptic population.
Putin had been due to travel to Tajikistan's capital Dushanbe for a regional summit later this week but in a call with President Emomali Rakhmon said he would not be able to attend in person, the Kremlin said.
Kremlin spokesman Dmitry Peskov told reporters that Putin was "absolutely healthy" but will not be attending in-person events.
He did not specify how long the president will be self-isolating for and declined to say who in Putin's entourage had tested positive.
When asked whether Putin had taken a coronavirus test and if it was negative, Peskov replied: "Undoubtedly".
It is unclear whether the president -- who says he has been vaccinated with Russia's homegrown Sputnik V jab -- will still be self-isolating during parliamentary polls scheduled for 17-19 September.
In his first public comments after the announcement, Putin said he "hoped" Sputnik V will protect him from the coronavirus.
"This is a natural experiment, let's see how Sputnik V will work in practise," Putin said, taking part in a government meeting via video link.
He added that one of the people who fell ill was vaccinated and tested positive days after getting a booster jab.
Russian authorities have taken exceptional measures to protect 68-year-old Putin since the start of the pandemic.
Foreign leaders, journalists and officials have all been required to self-isolate in advance of being in contact with Putin and a disinfection tunnel was installed at his residence outside Moscow.
The Russian leader said in late June that he was vaccinated with Sputnik after months of secrecy around the issue, but the Kremlin did not show images of the inoculation.
In recent months, the longtime Russian leader had resumed his work trips and face-to-face meetings, but many of his contacts are still required to spend two weeks in quarantine.
Putin on Monday met with Syrian President Bashar al-Assad and with Russian athletes returning from the Tokyo Paralympic Games.
Russia is among the countries hardest-hit by the coronavirus pandemic -- with the fifth-highest number of recorded cases according to an AFP tally -- and has struggled to rein in infections despite easy access to vaccines.
Infections have been falling in recent days after a spike in August, but health officials still reported 17,837 new cases and 781 new deaths on Tuesday.
Authorities have struggled with a vaccine-sceptic population, with independent polls showing that a majority of Russians do not plan to be inoculated.
As of Tuesday, about 39.9 million of Russia's 146 million people had been fully vaccinated, according to the Gogov website, which tallies Covid data from the regions.
Russia has several homegrown vaccines freely available to the public, but does not distribute any Western-made jabs.
Moscow, the epicentre of Russia's outbreak, and a host of regions have introduced mandatory vaccination measures to speed up the inoculation drive, and Putin has repeatedly called on Russians to get vaccinated.
Russian authorities have been accused of vastly downplaying the effects of the pandemic and, after a tight first lockdown in 2020, have refrained from introducing restrictive new measures.
As of Tuesday the country had recorded 7,176,085 cases and 194,249 fatalities, the highest death toll in Europe.