Despite the excitement over new, highly effective cures for the hepatitis C virus (HCV), health advocates warn that between 23,000 and 46,000 U.S. children are living with HCV—and that federal regulations and a lack of testing are denying them access to new drugs, Healthline reports.

The latest hep C treatments, such as Gilead Science’s Sovaldi (sofosbuvir) and Harvoni (sofosbuvir/ledipasvir), are proven to be far more effective, have fewer side effects and take less time than older therapies. However, since the cures have only been tested and approved for use in adults, children in need are stuck with older, more painful treatments.

Gastroenterologists are still advised to treat HCV-positive children with interferon and twice-daily oral ribavirin. Side effects for these drugs include severe depression, fatigue and even stunted growth. The treatment’s cure rate is also low among young people, coming in at just 45 percent.

Data shows only about 5 percent of HCV-positive mothers will pass the virus to their babies. About 40 percent of these children spontaneously clear the virus on their own. However, in about a quarter of HCV-positive children, the disease can progress quickly and require treatment.

Since the hep C treatment landscape is changing so rapidly, some liver experts argue for waiting to see which medications are the safest and most effective among adults before beginning clinical trials for children.