This is attributable to quasispecies heterogeneity. HCV constantly changes and mutates as it replicates – more than 1 trillion hepatitis C virions replicate each day. During the replication process, the hepatitis C virus will make ‘bad’ copies or errors in the genetic make-up of the newly replicated viruses. The process of constant mutation helps the virus escape the body’s immune response – when the dominant quasispecies is eradicated, another quasi-species emerges. This requires the immune system to constantly identify and kill the newly emerged variants. This is one of the reasons why so many people develop chronic disease. Scientists believe there are literally millions of different HCV quasispecies in everyone infected with hepatitis C, which are unique to everyone because of the individual’s immune response to HCV. This makes development of vaccine against HCV difficult.