title: Protection against persistence of hepatitis C.
abstract: BACKGROUND
  Neither previous hepatitis C virus (HCV) infection nor vaccination with HCV-derived antigens protects against reinfection. However, HCV infection and vaccination in chimpanzees has been shown to reduce the magnitude and duration of viraemia with re-challenge. We aimed to establish whether similar immunity could be achieved in man.
  
  
  METHODS
  From a study of injecting drug users, we identified 164 people who had no evidence of previous HCV infection and 98 individuals who had been previously, but were not currently, infected with HCV. We compared the incidence and persistence of HCV viraemia in these two groups over four consecutive 6-month periods.
  
  
  RESULTS
  Of participants without previous infection, the incidence of HCV infection was 21% (35/164). By contrast, people previously infected were half as likely to develop new viraemia (12% [12/98]), even after accounting for risk behaviour (hazard ratio, 0.45; 95% CI 0.23-0.88). Furthermore, in HIV-1-negative people, those previously infected were 12 times less likely than people infected for the first time to develop persistent infection (odds ratio 0.05, 95% CI 0.01-0.30), and median peak HCV RNA concentration was two logs lower. HCV persisted in six of six HIV-1-positive people, even in one man who had previously cleared HCV infection when he was HIV-1 negative.
  
  
  CONCLUSIONS
  There is an alarming frequency of HCV infection and persistence among injecting drug users. Our data suggest that immunity against viral persistence can be acquired, and that vaccines should be tested to reduce the burden of HCV-related liver disease.
authors: Department of Epidemiology, Johns Hopkins School of Public Health, Baltimore, MD, USA.
authors: Shruti H
authors: SH
authors: Mehta
authors: Andrea
authors: A
authors: Cox
authors: Donald R
authors: DR
authors: Hoover
authors: Xiao-Hong
authors: XH
authors: Wang
authors: Qing
authors: Q
authors: Mao
authors: Stuart
authors: S
authors: Ray
authors: Steffanie A
authors: SA
authors: Strathdee
authors: David
authors: D
authors: Vlahov
authors: David L
authors: DL
authors: Thomas
mesh_terms: D000328:Adult; D000410:Alanine Transaminase / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D015658:HIV Infections / Q000097:blood / Q000150:complications; D015497:HIV-1 / Q000276:immunology; D016174:Hepacivirus / Q000235:genetics / Q000276:immunology*; D006526:Hepatitis C / Q000150:complications / Q000276:immunology*; D006801:Humans; D018655:Lymphocyte Count; D008297:Male; D008875:Middle Aged; D012367:RNA, Viral / Q000097:blood; D015819:Substance Abuse, Intravenous; D013997:Time Factors; D014766:Viremia / Q000097:blood
chemical_list: D000914:Antibodies, Viral; D012367:RNA, Viral; D000410:Alanine Transaminase