Vaccine-Preventable Diseases

Hepatitis A is caused by the hepatitis A virus. Formerly called infectious hepatitis, it is usually spread by the fecal-oral route by either improper methods of personal hygiene or by the eating of contaminated foods, such as shellfish. This is a very common form of viral hepatitis, with approximately 1000 to 3000 cases reported each year in Canada. The worldwide annual incidence of hepatitis A now exceeds 1.5 million and the true number of cases of hepatitis A may be 3 to 10 times higher than reported. A vaccine is available to help protect against hepatitis A.

Hepatitis B is an inflammation of the liver caused by the hepatitis B virus. The virus may be found in blood and other body fluids, such as semen, vaginal secretions, saliva, and breast milk. Hepatitis B is usually spread by contact with infected blood or blood products; for example, through illicit I.V. drug use. Transmission of the disease can also occur through close interpersonal contact and by sharing blood-contaminated objects such as razors or toothbrushes which may accidentally cause breaks in the skin. In Canada, as in other countries, almost a third of infections have no identified risk factors. While most patients recover, the disease can be very serious and even fatal. Found throughout the world, it is most common in some African and Asian countries. In Canada, the overall incidence rate has been estimated to be 2.3 cases per 100,000 people or approximately 700 new cases per year. Hepatitis B can be prevented by vaccination.

The hepatitis C virus affects approximately 240,000 Canadians. It is one of the causes of what was previously called non-A, non-B hepatitis. Like the hepatitis B virus, the hepatitis C virus may be spread through contact with contaminated blood or possibly through household or sexual contact with an infected person. There is no vaccine currently available to help protect against hepatitis C.

Hepatitis D is caused by the delta virus, also known as the delta agent which is not a complete virus in and of itself. It can infect and cause illness only in persons who are already infected with the hepatitis B virus. When it does become active in the presence of hepatitis B virus, however, it is extremely dangerous. This virus is transmitted through the same routes as the hepatitis B virus. Currently there is no specific treatment available against hepatitis D virus, however, a hepatitis B vaccine which protects against hepatitis B virus infection may protect against presumable co-infection with hepatitis B virus and hepatitis D virus.