LONDON -- Scientists have shown that people can develop an immunity against persistent infection with the Hepatitis C Virus, raising hopes that a vaccine could reduce liver diseases linked to the virus.

In a report in the **** Lancet **** medical journal on Friday, researchers from Johns Hopkins University in Maryland described how intravenous drug users previously infected with the Hepatitis C Virus (HCV) were less likely to be re-infected than other drug users.

"The high rate of HCV infection in injecting drug users underscores the importance of preventing HCV infection," Reuters quoted Dr. David Thomas, who conducted the study, as saying

"Since it appears that immunity can be acquired to protect against viral persistence, vaccines should be tested to reduce the medical consequences of HCV infection among people at highest risk," he added.

Drug companies are conducting early trials of vaccines. Hepatitis C is a potentially fatal liver disease caused by the HCV, which is most common among drug users who inject illegal narcotics.

Former "Baywatch" star Pamela Anderson said in March she had contracted the disease by sharing a tattoo needle with her former husband Tommy Lee.

The illness causes jaundice, fatigue, abdominal pain, nausea and loss of appetite. An estimated four million people in the United States and 170 million worldwide are infected with HCV. About 85 percent of those infected will develop persistent infection and risk long-term complications including cirrhosis and liver cancer.

Antiviral drugs such as interferon are approved for the treatment of Hepatitis C

In the **** Lancet **** study, the incidence of HCV infection was nearly halved in drug users who had been previously infected compared to those who had not.

The findings are consistent with earlier research done on chimpanzees.