Update: The Moscow health department has denied plans to quarantine Muscovites with positive antibody test results. The proposal has been rejected and appeared online by mistake, an unnamed participant at the May 12 clinical council told the Business FM radio station.

Moscow authorities could place people who test positive for coronavirus antibodies into a two-week quarantine as part of the Russian capital’s mass testing program, the Kommersant business daily reported Thursday.

Moscow launched its campaign to build “herd immunity” last Friday, saying they will invite around 70,000 randomly selected people every three days for tests. The city is the epicenter of Russia’s Covid-19 outbreak with 155,219 out of 317,554 confirmed cases.

A Moscow health department clinical committee proposal dated May 12 recommends extending the isolation period for antibody-positive people to three weeks depending on “the specifics of the clinical process,” Kommersant reported.

Those who test negative for antibodies are urged to follow general guidelines for preventing infection.

The committee is comprised of the Moscow health department’s freelance experts and chief doctors from the city’s coronavirus hospitals, Kommersant reported. Its recommendations on Covid-19 prevention, diagnosis, treatment and rehabilitation are not published in the public domain.

The Chinese-made antibody tests have a 96.26% sensitivity and 95.38% specificity, said Russia’s molecular diagnostics website PCR News, which first published the committee’s proposal Wednesday.

Russia’s Internet giant Yandex offered a free testing service at home for a few weeks in late April and early May and says it tested 20,000 people. It has since halted the service, saying free tests are now easily accessible elsewhere.

Moscow Mayor Sergei Sobyanin has estimated that the real number of coronavirus infections amounts to 2.5% of the capital’s population of 12.5 million, or around 300,000 people.

Experts warn that a positive antibody test does not confer total immunity to Covid-19 as some countries move to introduce “immunity passports.”