Which one of the following diseases cannot be prevented by vaccination?

Hepatitis C is a viral infection caused by the hepatitis C virus (HCV), and currently, there is no vaccine available to prevent this disease. Unlike some other viral infections, there has been no effective vaccine developed despite ongoing research efforts. Infection typically occurs through contact with infected blood, and while treatment options exist, the focus on prevention has not yet yielded a vaccination solution.

In contrast, the other diseases listed, such as chickenpox, tetanus, and tuberculosis, all have established vaccines that can significantly reduce the incidence and severity of these illnesses in populations. Vaccination remains one of the most effective measures for controlling the spread of these diseases and protecting individuals against them.