HCV – The Mystery Without a Vaccine

In modern medicine, where vaccines against various viruses have become almost routine—especially after the global COVID-19 pandemic—it seems almost unbelievable that hepatitis C, a serious chronic viral liver infection, still has no vaccine. Despite decades of intensive research and significant scientific efforts, HCV remains one of the few known viruses for which a preventive immunization has not yet been developed.

The hepatitis C virus is transmitted almost exclusively through blood. The most common routes of infection include the use of non-sterile needles, sharing of injection drug equipment, blood transfusions carried out before routine testing was introduced, and, in some cases, risky medical or dental procedures in settings with poor sterilization practices. Although sexual transmission is possible, it is less common, and the virus can also be transmitted from mother to child during pregnancy or childbirth. In many cases, people remain unaware of their infection for years, as the disease often causes no symptoms until significant liver damage has already occurred.

The fact that the disease often remains "silent" for so long makes HCV particularly dangerous. Many people only learn about their infection when symptoms like cirrhosis, chronic fatigue, jaundice, or abdominal pain appear—by which point the liver may already be seriously damaged. Long-term, untreated infection significantly increases the risk of developing hepatocellular carcinoma, one of the most severe forms of liver cancer.

Despite the severity of the disease, scientists have faced numerous obstacles in developing a vaccine. The biggest challenge is the virus’s extraordinary ability to mutate. HCV has a highly unstable genetic structure, resulting in constant changes to its surface proteins. These proteins are the parts the immune system would normally recognize and target. However, due to their variability, the immune system struggles to identify and remember them. As a result, a vaccine that may be effective today could quickly become ineffective as new viral variants emerge.

Moreover, there are at least seven major genotypes of HCV, each of which includes multiple subtypes. These genotypes are not evenly distributed around the world—some are more common in Asia, others in Europe, Africa, or North America. This geographic and genetic diversity adds another layer of complexity to creating a universal vaccine.

Another key issue is that natural infection does not provide lasting immunity. People who recover from hepatitis C can become reinfected, even with the same genotype. This suggests that the human immune system does not mount a strong or long-lasting response to the virus, making it difficult for scientists to identify a reliable “template” for vaccine development. HCV also has sophisticated mechanisms for evading the immune system. It can interfere with the function of T-cells—critical for viral defense—and weaken the effectiveness of antibodies. This makes the virus exceptionally elusive, not only to our natural defenses but also to artificial attempts to enhance those defenses through vaccination.

Despite these challenges, medicine has made remarkable progress in treating hepatitis C. Today, direct-acting antiviral drugs (DAAs) specifically target viral enzymes and can cure the infection in over 95% of cases, often within just 8 to 12 weeks. This marks a dramatic improvement over older interferon-based therapies, which were long, exhausting, and had numerous side effects.

Still, treatment is not a substitute for prevention. These medications remain expensive and often inaccessible in low- and middle-income countries. Moreover, individuals who have been cured are not immune and can be reinfected. Without a vaccine, the virus continues tobcirculate, especially among high-risk populations. Vaccination remains the only truly effective strategy for halting transmission and moving toward the global elimination of hepatitis C.

For this reason, efforts to develop a vaccine continue. Modern research includes mRNA technology, vector-based vaccines, and experimental strategies that target multiple genotypes at once. Although progress is slow, there is reason for optimism. Every new insight into the virus’s behavior, immune response, and genetic makeup brings us one step closer to a solution with global impact.

The fight against hepatitis C is a story of persistence and patience—a battle between a virus that constantly evolves and a scientific community that refuses to give up. While we have not yet reached the finish line, it is increasingly clear that an HCV vaccine is not a question of possibility, but of time. And when that moment arrives, it will mark one of the most important triumphs of modern medicine in the field of infectious diseases.

Halima Čaušević

Faculty of Health Studies

Universitiy of Sarajevo

2024/2025 BOSANA Scholarship holder