BALTIMORE, April 25 (UPI) -- People who have recovered from the hepatitis C virus may have developed some immunity to future infections, according to a study released Thursday from the medical journal, The Lancet.
The results are important because they may pave the way for development of a vaccine to prevent hepatitis C, the researchers said. Currently, there are no hepatitis C vaccines, and available treatments are effective for less than half of those who get the virus.
The findings indicate "natural infection may be protective, which means that maybe we could devise a vaccine that results in similar protection," Stuart Ray, assistant professor of medicine at Johns Hopkins University in Baltimore and co-author of the study, told United Press International.
The study "is important for vaccine development because it says if a person is infected and they clear the virus and they're reinfected, they're not going on to become a chronic carrier," Lesley Johnson, chief of the enteric and hepatic diseases branch at the National Institutes of Health's Institute of Allergy and Infectious Diseases in Bethesda, Md., told UPI.
Ray noted previous work with vaccines in chimpanzees with human hepatitis C have yielded disappointing results because the animals still could be reinfected with the virus.
"If virus was detected in the chimps' blood, then that would be considered a failure ... but this research suggests that vaccines may prevent chronic infection and that may be enough," Ray said.
This means a vaccine could be developed that may not block infection with hepatitis C but would enable people to clear the virus and not become chronic carriers, said Johnson, who was not involved in the study.
Preventing chronic infection would be a significant achievement because it could lessen the risk for developing cirrhosis and liver cancer, caused by the virus only in people with persistent hepatitis C infection.
About 85 percent of the 4 million people in the United States and 170 million worldwide who are infected go on to develop persistent infection.
Ray and colleagues followed for two years 164 injecting drug users in Baltimore who had never had hepatitis C and 98 who had been infected in the past but were not currently carrying the virus. Those who previously had been infected were half as likely as those who had never been infected to develop a new hepatitis C infection.
The numbers were even more striking for those who were HIV-negative. Those previously infected with hepatitis C were 12 times less likely to develop persistent infection than those infected with the virus for the first time.
The drugs interferon and ribavirin can effectively treat about 40 percent of people with hepatitis C but they may be too expensive in developing countries where it is a major health problem. Researchers said that makes it all the more urgent to develop an effective vaccine.