Criminals are looking to cash in on the U.S. immunization push against COVID-19 by selling forgeries of government-issued 'vaccination record cards' that show people have been inoculated. Hundreds of fraudsters are selling blank or forged versions of the cards over ecommerce sites including eBay, Etsy and Shopify, while also running advertisements for the fakes on Facebook, according to Saoud Khalifah, CEO of Fakespot, which uses artificial intelligence to detect online retail scams. And with names such as blankcovidcard.com, such sellers are hardly discreet. 'In January we started noticing Shopify stores selling fake vaccination cards, and that was really interesting because it introduced a new dynamic to society where people can counterfeit immunity and interplace it with a fake card,' Khalifah told CBS MoneyWatch. 'It's a new concept we haven't seen before.' Fakespot has identified hundreds of different sellers that have cropped up since the beginning of the year, and the firm estimates they've hawked thousands of false records over the past three months. Online retail sites have banned some bad actors, who then often reappear and sell fake cards under different names, according to Khalifah. The low-tech vaccine records are easy to replicate. The 4-by-3-inch, double-sided paper cards bear the logo of the federal Centers for Disease Control and Prevention in black and white, along with a cardholder's name and birthdate. They also note the drugmaker, lot number, and date and location for the administered vaccine. The information is annotated either in pen or on a printed sticker. One seller, whose Shopify store is now defunct, was selling a pack of four blank vaccination cards for $80. Prosecutors call for action Shopify, a platform that allows retailers to create ecommerce sites, said it has acted swiftly against users of its technology who are trying to sell fraudulent vaccine cards. Hawking bogus cards violates the company's policies, the company told CBS MoneyWatch, noting that it has been monitoring its platform for such schemes since February. The National Association of Attorneys General last week called on eBay, Shopify and Twitter to stop people from selling or advertising fake CDC vaccine cards on their platforms. To date, Shopify has terminated three stores it found to be selling fake or blank vaccination cards, or fraudulent vaccine stamps. 'If our search identifies a potentially prohibited product, our team swiftly reviews the store and product and takes appropriate action,' Vivek Narayanadas, Shopify's vice president of legal, wrote in a letter to the National Association of Attorneys General. 'All stores that we identified for violating our policies were actioned swiftly,' Narayanadas said in a statement to CBS MoneyWatch. Etsy also confirmed that the sale of phony vaccine cards violates the site's rules and that it is removing any posts advertising the fake records. EBay said it blocks or quickly removes items on its marketplace that make false health claims, 'including vaccine ID cards or any simila