Can Vaccines Prevent Cancer?
HEPATITIS B & LIVER CANCER
Hepatitis B is the most serious form of viral hepatitis. Infection causes inflammation of the liver and death of liver cells. The liver cells regenerate. If the chronic infection is too severe, the growth of cells can be substantial. Mutations can happen in the growing cells, eventually leading to cancer. In Asia, before the introduction of the vaccine most people became infected in childhood and 8–10% of the general population was chronically infected. Preventing childhood infection by vaccination, and thus preventing chronic disease, reduces the incidence of liver cancer significantly. The vaccine against Hepatitis B is the first vaccine against cancer and is now routinely given to infants.
The virus is transmitted by blood, most commonly from mother to baby at birth, through child-to-child transmission, via non-sterile injections, and through unprotected sex. Although most infections are from mother to child, sharing needles is a major contributor to spreading the disease. Blood used for transfusions is screened to be sure that Hepatitis B and other infectious agents are not present. As with many viral diseases, prevention by vaccination is more effective than treatment with drugs.
Cervical cancer is on a growing list of cancers, including nasopharyngeal cancers, lymphomas, and gastric cancer, that are caused by infectious diseases. Cervical cancer accounts for 15% of all cancer deaths in developing countries and can be prevented by vaccination against human papillomavirus (HPV). As additional links between cancers and infectious diseases are discovered, new opportunities for preventing chronic diseases by vaccination are likely to increase.
The human papillomavirus has been linked to cervical cancer and can be prevented by vaccination. (Image courtesy of Dr. Stephen Harrison)