Although sexual transmission of hepatitis C virus (HCV) has not been definitively established, the strongest evidence for this route of transmission comes from epidemiologic studies of non-A, non-B hepatitis. Studies of the prevalence of antibodies to HCV (anti-HCV) among persons who are at risk for this disease have been conflicting. Thus, no recommendations have been made about immune globulin prophylaxis for sexual partners of infected persons. Piazza and associates studied the risk of sexual transmission of HCV and evaluated the efficacy of immune globulin prophylaxis in preventing transmission of the infection to sexual partners.

The randomized, controlled trial included 899 heterosexual partners of persons positive for anti-HCV; 64.3 percent of the partners were women. The partners were randomized to receive 4 mL of immune serum globulin, prepared from unscreened donors, or placebo, every two months. Tests for HCV infection were performed every four months. A total of 884 subjects completed the study.

Seven sexual partners (four women and three men) developed HCV infection as documented by test results positive for HCV RNA. Six persons were in the placebo group and one was in the prophylaxis group. The risk of acquiring HCV infection was significantly higher in the control group. In untreated partners, the relative risk of becoming positive for HCV RNA was 10.7. None of the members of the placebo group who became infected had been exposed to any parenteral risk factors.

Anti-HCV and HCV RNA tests were conducted every six months during follow-up of partners who became infected. Follow-up ranged from 20 to 24 months. All of the infected partners had persistent viremia. Two persons became symptomatic. After 20 months, four of the seven infected partners underwent liver biopsy, which revealed chronic active hepatitis. Sequence homology studies strongly suggested sexual transmission of HCV.

The authors conclude that these study results demonstrate that HCV can be sexually transmitted. HCV transmission occurred only in the partners of HCV-infected patients with active liver disease. The sexual partners who acquired HCV infection during the study tended to be older (54 years versus 43 years) and tended to have a longer sexual relationship (27 years versus 18 years) with the infected person. Until the introduction of a vaccine for HCV, the authors believe that immune globulin prophylaxis may afford significant protection against sexual transmission of HCV.