A vendor on Amazon was discovered selling a pack of blank COVID-19 vaccination cards this week. The post has since been removed, but photos reshared online showed a 10-pack of blank cards going for $12.99.

In the U.S., actually getting a COVID-19 vaccine and receiving a legitimate vaccination card is free.

The small white piece of cardstock given to Americans after receiving all necessary COVID-19 shots is the only official way to show some proof of full immunization on the fly. But according to the Federal Trade Commission, those simple cards, easily replicated by fraudsters, never were designed to prove vaccination status long term.

Other vendors selling fake vaccine cards have cropped up on Etsy, an e-commerce site focusing on handmade and vintage items; on pro-Trump forums; and on the dark web, according to recent reports.

"We do not allow the products in question in our store. We have proactive measures in place to prevent prohibited products from being listed and we continuously monitor our store," an Amazon spokesperson said in an email to NPR. "In this case, we have removed the items and taken action on the bad actors involved in bypassing our controls."

Etsy didn't immediately respond to NPR's requests for comment.

A black market for fake vaccination cards has grown in the waning days of the pandemic in the U.S. and other parts of the world. Authorities have been warning about the rise in pandemic-related fraud for months.

Fake vaccine cards not only have a negative impact on public health, the FBI said, but they're against the law — unauthorized use of an official government agency's seal can be punished with a fine or up to five years in prison.

The FBI said earlier this year, "By misrepresenting yourself as vaccinated when entering schools, mass transit, workplaces, gyms, or places of worship, you put yourself and others around you at risk of contracting COVID-19."

The FBI and Justice Department didn't immediately respond to a request for comment on potential investigations into such schemes.

State attorneys general set their sights on the issue in April, urging tech CEOs to nip this phenomenon in the bud before it got worse.

In April, 47 members of the National Association of Attorneys General sent the CEOs of Twitter, Shopify and eBay a letter requesting that they take immediate action on bad actors spreading COVID-19 misinformation and using the sites to sell fake vaccine cards.

The letter read, "The false and deceptive marketing and sales of fake COVID vaccine cards threatens the health of our communities, slows progress in getting our residents protected from the virus, and are a violation of the laws of many states."

A coalition of 42 attorneys general sent a separate letter later that month to OfferUp, an online mobile marketplace, requesting similar action after fraudulent and blank COVID-19 vaccine cards were discovered being sold on the platform. One pack of vaccine cards was being sold for $40.

Efforts are being made to prevent fraud

Catching and charging people behind the selling of fake COVID-19 immunization cards has been rare so far.

California bar owner Todd Anderson was arrested last month for allegedly selling fake COVID-19 vaccination cards in what was believed to be the first thwarted scheme of its kind.

Anderson was charged with identity theft, forging government documents, falsifying medical records and having a loaded, unregistered handgun.

In Long Island, a now-former CVS employee was caught with dozens of COVID-19 vaccination cards that he planned to provide to family and friends.

In response to those cases, New York legislators started the process of making it a felony to forge or possess fake immunization records, including COVID-19 cards. Last week, the New York State Senate passed legislation, S.4516B.

Bill sponsor Sen. Anna M. Kaplan said in a press release, "We're already seeing anti-vaxxers spread tips online for how to create fake cards in order to get around vaccination mandates, and we need to put a stop to this effort to defraud the public so that our recovery from the pandemic can keep moving forward."