Iowa State University researcher, Dr. Dong-Pyou Han, resigned after news broke of an investigation into the validity of his AIDS research. Han is believed to have tampered with research results for a possible AIDS vaccine.

“At Iowa State’s request, the research samples in question were examined by researchers at another university; they confirmed samples had been spiked,” ISU spokesman John McCarroll wrote in an email to the Des Moines Register. “He later admitted responsibility and resigned from Iowa State, effective Oct. 4, 2013.”

When McCarroll says the samples were “spiked,” he means that they were inauthentic. The study that Han conducted was supposed to be based on monitoring rabbits’ reaction to the proposed vaccine treatment. The findings showed that the rabbits’ blood produced HIV-resistant antibodies. However, upon further investigation, the university and the National Institutes of Health (NIH) found that Han added human blood to the rabbit blood to positively skew the results.

Han’s “discovery,” which was touted as a breakthrough in AIDS research, generated $19 million in federal grants over the years. On Monday, a notice in the Federal Register said that Han gave a “detailed admission” of fault in the case. Han entered a Voluntary Exclusion Agreement, which prohibits him from contracting with any agency of the United States government for a period of three years. He is also excluded from serving in any advisory capacity to the U.S. Public Health Service.

There is no word yet on whether the government is going to press charges.

"It's unusual to see someone fake results this brazenly," said physician and medical journalist Ivan Oransky, according to USA Today. "This is fraud, and the question is whether it's a big enough case for the government to go after. ... I think it's time for the government to criminally prosecute more of these cases."