There is currently no vaccine to protect against hepatitis C infection, which can cause severe liver damage. But early results of an experimental vaccine appear promising, researchers report in the journal Science Translational Medicine.

Hepatitis C mutates easily, like HIV, and has been considered very difficult to protect against.

British and Italian scientists treated 41 volunteers with the vaccine, which is designed to stimulate a T-cell response against the virus’ internal proteins – instead of the usual approach of creating an antibody attack against the virus’ constantly mutating outer coat.

The inside of the virus is much more stable than its outside, explained the study’s lead author Dr. Paul Klenerman, a senior research fellow at Oxford University’s Nuffield Department of Clinical Medicine.

Researchers found cells in all 41 study subjects indicating immunity to the virus was present for a year. This suggests the subjects’ immune systems were prepared to respond if faced with the hepatitis C virus.

While this research focused on the vaccine’s safety, more clinical trials are necessary to test the vaccine’s protective abilities, researchers note. Even if the vaccine is found to be safe and effective, the question remains as to whether it will protect against different strains of hepatitis C.

An estimated 170 million people worldwide are afflicted with hepatitis C. Those at risk for hepatitis C infection include people in regular contact with blood, on long-term kidney dialysis, and those who use injectable street drugs, according to the U.S. National Institutes of Health.