Will There Be a Vaccine to Protect Against the Hepatitis C Virus?

Abstract

The discovery of the hepatitis C virus (HCV) more than 20 years ago offered the promise of a vaccine to prevent life-long persistent infection and associated progressive liver diseases. To date, only a few candidate vaccines have been tested in human beings for safety and immunogenicity. None have yet been assessed for prevention of HCV infection or persistence. In the event that current vaccine candidates do not advance to efficacy trials, or fail to provide protection against HCV, the pipeline of alternatives appears to be very small. With a sharp reduction in new HCV infections because of effective screening of the blood supply, and the possibility that acute and chronic infections will be curable because of improving therapy, 1 it is reasonable to ask if the considerable effort to develop a preventive HCV vaccine still is needed. The answer is almost certainly affirmative. Vaccines that protect against hepatitis A and B virus infections were first targeted to health care workers. The value of adding a vaccine to prevent accidental HCV infection in the workplace is clear. A preventive HCV vaccine would have a far greater impact on public health. The need is highlighted by a concerning increase in new infections among adolescents and young adults recently observed in Massachusetts. Between 2002 and 2009, confirmed HCV cases shifted from a unimodal to bimodal age distribution because infection rates increased among those aged 15‐24 years, however, they continued to decline among older adults. 2 The increase in new HCV infections in the younger age group is attributable to needle sharing and probably will be confirmed elsewhere in the United States and in other countries. Without a preventive vaccine it will be difficult to contain a smoldering epidemic of unrecognized HCV infections involving those who are least likely to seek or receive antiviral therapy, no matter how effective. A vaccine also would be highly beneficial in regions of the world with high HCV endemicity, for instance, in countries such as Egypt where it has proved difficult to interrupt several decades of HCV transmission by standard public health measures.3 When considering the need for a vaccine, it is important to remember that symptoms of acute hepatitis are often mild or inapparent, therefore years can elapse before infection is recognized and treated. Serious liver disease can develop during that time and the infection remains transmissible to others by high-risk practices. Perhaps as importantly, only a very small percentage of HCV infections were ever treated with pegylated type I interferon and ribavirin. 4 New direct-acting antivirals will improve this situation, but only with a much greater effort to diagnose the large number of unrecognized infections and provide access to costly treatment that must be managed carefully to prevent emergence of resistant viral variants.