Two recent studies out of Stanford Medicine found that only two thirds of patients with hepatitis C receive medications known as direct-acting antivirals (DAAs), which cure infection in most people living with the virus. Left untreated hepatitis C can progress to scarring of the liver (cirrhosis and fibrosis) and even liver cancer.

Spread via contact with blood, hepatitis C affects over 2 million people in the United States. DAAs, which target the virus’s proteins, are effective in eliminating the viral infection in about 97% of patients.

“It’s sad that a treatment proven to be so effective is used by only a fraction of the diagnosed people,” said the senior author of both papers, Mindie Nguyen, MD, professor of gastroenterology and hepatology at Stanford University, in a news release.

The studies analyzed more than 100,000 adults with chronic hepatitis C who had private insurance. One of the studies, published in JAMA Internal Medicine, found that patients treated with DAAs had a much lower risk of developing liver-related conditions, such as decompensation, which deteriorates liver function, and liver cancer, compared with untreated patients: 27% versus 64%. What’s more, the mortality rate for treated patients was about half (43%) that of the untreated.

“Treatment clearly decreases the risk of liver cancer and improves survival in people,” Nguyen said.

The second study, published in JAMA Network Open, found that only 65% of privately insured Americans received treatment from April 2018 to March 2019.

“The benefits are clearly shown in our study. We are looking at a population with probably better coverage than anyone—patients in the United States with private insurance—yet less than 65% of people diagnosed with hepatitis C received treatment,” she continued. “That is quite sobering.”

The out-of-pocket cost of treatment (sometimes thousands of dollars even with insurance) is likely one strong deterrent, according to Nguyen, who speculates that the time it takes to complete the additional testing sometimes required prior to treatment may also serve as a barrier to many patients.

“There needs to be a better public campaign that reaches out to the people who may be more resource limited: those in rural areas and immigrant communities,” Nguyen said. “Insurance reimbursement should remove the barriers. It’s as easy as writing a prescription for antibiotics.”