BOSTON — Interferon is the first treatment to relieve and even cure lingering hepatitis B infections, the leading cause of cirrhosis and liver cancer and one of the world’s biggest killers, researchers have found.

A study found that injections of the natural protein can stop the hepatitis B virus from destroying the liver in almost half of the people who are chronically infected. One in 10 is cured.

Until now, there has been no treatment for the hepatitis B virus. While interferon clearly does not help everyone, having any therapy at all is considered to be an important step in controlling this infection.

“This is an encouraging result. All of us would feel a lot happier if we had a better treatment. This spurs us on to find that,” commented Dr. Baruch S. Blumberg of the Fox Chase Cancer Center in Philadelphia. He won the Nobel prize in medicine in 1976 for identifying the hepatitis B virus.

The latest research, conducted on 169 people at 12 hospitals, is the first large-scale comparison study of interferon for hepatitis B. It confirms several smaller studies suggesting that the treatment works.

Other studies also have shown that interferon works against hepatitis C, another serious but less common variety of the virus. On Tuesday, an advisory committee of the U.S. Food and Drug Administration recommended that interferon be marketed for hepatitis C.

Doctors said the latest study is big enough so physicians can use the results to predict how interferon will affect their patients if — as seems likely — it becomes the standard medicine for hepatitis B.

“We can be relatively sure what doctors will find in practice: Ten percent will be cured and 40 or 50 percent will be made better and their liver disease will be stopped in its tracks,” said Dr. Robert P. Perrillo of the St. Louis Veterans Affairs Medical Center, the principal author of the study.

The results were published in Thursday’s New England Journal of Medicine along with an editorial by Dr. Jay H. Hoofnagle of the National Institute of Diabetes and Digestive and Kidney Diseases.

“For now, interferon alpha offers the best hope” for treating chronic hepatitis B, Hoofnagle wrote.

Experts cautioned that the treatment should be used only for those with chronic infections who show signs of liver damage.