Around 14% of Russians tested for the coronavirus have developed immunity to the infection, Interfax reported Wednesday, citing health officials.

Almost 650,000 Russians have been tested for the virus across 46 regions of the country, the head of Rospotrebnadzor, Russia’s consumer protection watchdog, was cited as saying.

“The percentage of immune cases among minors under 17 years old is almost 20%,” Rospotrebnadzor head Anna Popova said at a meeting of the government’s coronavirus response team.

“For people between 18 and 64 years old, it’s 14% and only 11% for those 65 years and older,” she said.

The World Health Organization’s (WHO) director of public health Maria Neira said immunity from coronavirus lasting between six months and a year is “expected” among patients who have developed antibodies.

Experts warn that antibodies do not necessarily confer total immunity against the virus, however.

Popova’s cited results are identical to an analysis of more than 40,000 voluntary tests published by a Moscow-based private lab last month. The lab, Invitro, 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.

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

There have been 493,657 cases of coronavirus infection reported in Russia so far and 6,358 deaths.