One out of seven healthy Russians may have been infected with the coronavirus, according to a Moscow-based private lab analysis of voluntary testing published Friday.

Out of more than 40,000 people tested between Monday and Thursday in most Russian regions, the Invitro lab said 14% had antibodies. Nearly half of Invitro’s tests were submitted in Moscow and the Moscow region, the epicenter of Russia’s coronavirus outbreak. 

“Data on the presence of specific antibodies provide valuable information needed to make societal and individual clinical decisions,” Invitro’s medical director Natalya Kolesnikova said in a press release.

The lab said its Russian-made tests have 95% sensitivity and 98% specificity for an antibody that develops up to four weeks after people first come into contact with the virus.

Experts including Invitro warn that antibodies do not necessarily confer immunity against the infection.

Invitro said it will publish real-time data broken down by geography and demographics on its website.

Moscow’s mayor has previously suggested that up to 2.5% of residents, or nearly 300,000 people, may have been infected with Covid-19.

Last Friday, he announced that the city will launch mass random testing for Covid-19 antibodies. The free and voluntary testing will “show the real picture” of the epidemic’s stage, since many people may have had the virus without knowing it, Sergei Sobyanin told state television.

Officials said last week that 21% of Russian medics, who were among the first to submit tests, were found to have antibodies.

There have been 326,448 cases of coronavirus infections reported in Russia so far and 3,249 deaths. More than 30% of patients have recovered.