In the days before President Joe Biden announced all private sector businesses with more than 100 employees would have to require their employees be fully vaccinated, fake vaccine cards cost approximately $100. The day after his announcement last week, fake vaccine card prices doubled to $200.

The number of sellers peddling bogus cards also went up, spiking from 1,000 to more than 10,000 sellers, security researchers at Israeli security firm Check Point, which was founded by veterans of an elite cyber unit of Israel’s military intelligence directorate, tell The Daily Beast.

The number of subscribers in Telegram groups oriented towards fake vaccine cards has grown by a multiple of five, the researchers, who monitor the darknet and deep web, said.