Medicare spent more than $4.7 billion treating hepatitis C last year—and new drugs, including Gilead’s Sovaldi and Harvoni and Johnson & Johnson’s Olysio, accounted for most of it. “The spending dwarfs the approximately $286 million that the program, known as Part D, spent on earlier-generation hepatitis C drugs in 2013,” ProPublica said in its report.

Older hepatitis-C medications accounted for $157 million of last year’s total. Newer Sovaldi accounted for more than $3 billion and Harvoni, which became available in October, accounted for $670 million. Olysio, which is used in conjunction with Sovaldi, contributed $821 million.

Although some research indicates these newer drugs can prevent costly treatments—such as liver transplants later in the treatment cycle—this may not be true for Medicare patients. ProPublica noted that the Annals of Internal Medicine recently published a study that showed that these new drugs would only offset about 25% of the $65 billion government programs—not just Medicare—are expected to spend on the drugs.