Moscow has launched a mass screening programme for coronavirus antibodies, inviting people chosen at random from various age groups to clinics across the city.
The hope is that the test results can allow the authorities to map their way out of lockdown, despite uncertainty over how much immunity to Covid-19 the antibodies actually provide.
Three dozen Moscow clinics are collecting intravenous blood samples, which are sent to laboratories for analysis overnight.
Russian doctors believe the method, known as IFA, is more accurate than express-testing used elsewhere.
It identifies the Immunoglobulin M antibody (IgM), which appears when the body is fighting a new infection, and Immunoglobulin G (IgG) which shows that someone has previously been infected.
Swabs for Covid-19 itself are taken at the same time.
Free tests will be given to 70,000 people every three days, allowing Moscow to build a much clearer picture of the spread of the virus since the start of the epidemic – as well as isolating anyone who is sick, but didn’t realise it.
This is in addition to widespread coronavirus testing of those with symptoms that’s already taking place.
“If that’s what’s needed, then it’s needed,” one man who had received a text-message inviting him for testing told the BBC. “The main thing is that it’s free!”
Vladimir Putin this week announced that the full nationwide lockdown was over, instructing regional leaders to decide when to lift specific restrictions.
Moscow’s mayor has described that as the “most difficult decision” of his life, and schools and playgrounds, bars and many businesses remain closed until at least 31 May.
Russia currently has one of the world’s highest rates of coronavirus infection, with 10,598 new cases detected on Friday.
