As the delta variant of the coronavirus sweeps across the United States, a growing number of colleges and universities are requiring proof of COVID-19 vaccination for students to attend in-person classes. But the new mandate has opened the door for those opposed to getting the vaccine to cheat the system, according to interviews with students, education and law enforcement officials.

Across the internet, a cottage industry has sprung up to accommodate people who say they won’t get vaccinated for either personal or religious reasons.

An Instagram account with the username “vaccinationcards” sells laminated COVID-19 vaccination cards for $25 each. A user on the encrypted messaging app, Telegram, offers “COVID-19 Vaccine Cards Certificates,” for as much as $200 apiece.

An increasing number of inquiries to these sites and similar ones appear to be from those who are trying to get fake vaccination cards for college.

A Reddit user commented on a thread about falsifying COVID-19 vaccination cards, saying, in part, “I need one, too, for college. I refuse to be a guinea pig.”

According to a tally by The Chronicle of Higher Education, at least 675 colleges and universities now require proof of COVID-19 inoculations. The process to confirm vaccination at many schools can be as simple as uploading a picture of the vaccine card to the student’s portal.

In Nashville, Vanderbilt University places a hold on a student’s course registration until their vaccine record has been verified unless they have an approved medical accommodation or religious exemption.

The University of Michigan says it has checks in place to confirm employee and student vaccinations. A spokesman told The Associated Press the school has not encountered any problems so far with students forging their COVID-19 vaccination record cards.

But Benjamin Mason Meier, a global health policy professor at the University of North Carolina at Chapel Hill, questions how institutions can verify those records.

“The United States, unlike most countries which have electronic systems in place, is basing its vaccination on a flimsy paper card,” he said. “There need to be policies in place for accountability to make sure that every student is operating in the collective interest of the entire campus.”

In a statement to AP, UNC said the institution conducts periodic verification of documents and that lying about vaccination status or falsifying documents is a violation of the university’s standards and may result in disciplinary action. The school said it had not found any instances of a student uploading a fake vaccine card.

But other university staff and faculty have expressed their concern. Rebecca Williams, a research associate at UNC’s Lineberger Comprehensive Cancer Center and Center for Health Promotion and Disease Prevention, said while she is concerned by these claims, she isn’t surprised.

“This is why I think the development of a reliable national digital vaccine passport app is very important for the sake of all the organizations and businesses that want to require proof of vaccination for employees, students, or business patrons,” Williams said.

The AP spoke with students across the country who did not want to be identified but said they were aware of attempts to obtain fake cards.

Some school officials acknowledge it’s impossible to have a foolproof system.

“As with anything that potentially requires a certification, there is the possibility for an individual to falsify documentation,” said Michael Uhlenkamp, a spokesman for the chancellor’s office at California State University. The school system, the largest in the nation, oversees about 486,000 students on 23 campuses.

In March, the concern over fake COVID-19 vaccination cards prompted the FBI to issue a joint statement with the U.S. Department of Health and Human Services urging people not to buy, create or sell fabricated vaccine cards. Unauthorized use of the seal of a government agency such as HHS or the Centers for Disease Control and Prevention is a federal crime.

In April, a bipartisan coalition of 47 state attorneys general sent a letter to the CEOs of Twitter, Shopify and eBay to take down ads or links selling the bogus cards.

Many of the sites have blacklisted keywords related to fake cards, but places to buy the documents are still popping up on messaging apps, chat forums and the dark web.

Sellers on websites such as Counterfeit Center, Jimmy Black Market, and Buy Express Documents list COVID-19 vaccine cards, certificates and passports for sale, some costing €400 Euros or about $473.49. An advertisement on the website Buy Real Fake Passport promises fake vaccination cards by the thousands.

“It is hiding under our noses. If you want it, you can find it out,” said Saoud Khalifah, founder and CEO of scam-detecting software Fakespot. “If we are seeing signs where things like Lollapalooza and other festivals are getting fake cards to gain entrance, the trend is just going to continue into these universities.”

In July, the U.S. Department of Justice announced its first federal criminal fraud prosecution involving a fake COVID-19 immunization and vaccination card scheme. Juli A. Mazi, 41, a naturopathic physician in Napa, California, was arrested and charged with one count of wire fraud and one count of false statements related to health care matters.

Court documents allege she sold fake vaccination cards to customers that appeared to show that they had received Moderna vaccines. In some cases, the documents show Mazi herself filled out the cards, writing her own name, and purported Moderna “lot numbers” for a vaccine she had not in fact administered. For other customers, she provided blank CDC COVID-19 vaccination record cards and told each customer to write that she had administered a Moderna vaccine with a specified lot number.

Requiring vaccinations to attend class at colleges and universities has become a contentious political issue in some states. Public colleges in at least 13 states including Ohio, Utah, Tennessee and Florida cannot legally require COVID-19 vaccinations due to state legislation, but private institutions in those same states can.

Some college students have taken to social media platforms like Twitter and TikTok to voice their outrage over other students possessing fraudulent vaccine cards.

Maliha Reza, an electrical engineering student at Pennsylvania State University, said it is mind-boggling that students would pay for fake vaccination cards when they could get the COVID-19 vaccine at no cost.

“I’m angry about that, like there is more anger than I could describe right now,” Reza said. “It’s dumb considering the vaccine is free and it is accessible across the country.”