Immunizations - Poliomyelitis

The hepatitis A virus infected an estimated 56,000 people in 2004. Hepatitis A, formerly called infectious hepatitis, is always acute and never becomes chronic. The virus is excreted in feces and transmitted by contaminated food and water. Eating shellfish taken from sewage-contaminated water is a common means of contracting hepatitis A. It can also be acquired by close contact with individuals infected with the virus. It is estimated that 11 - 16% of reported cases occur among children or employees in daycare centers or among their contacts. The hepatitis A virus does not directly kill liver cells, and experts do not yet know how the virus actually injures the liver.

A fly may act as a mechanical vector of diseases such as hepatitis A. The fly may carry the infective organism on its feet or mouth parts and contaminate food or water, which a person then consumes. A biological vector actually develops an infective organism in its body and passes it along to its host, usually through its saliva. A fly can be a biological vector, as in the transmission of leishmaniasis by the sandfly.

Vaccines for Hepatitis A

All children should get 2 doses of the hepatitis A vaccine starting at 1 year, according to CDC recommendations. The doses should be given at least 6 months apart. Others who should be vaccinated against hepatitis A include travelers to developing countries, people living in communities where outbreaks occur, people with blood-clotting disorders, sexually active homosexual men, and health care workers exposed to the virus. People with chronic liver disease, including those with hepatitis C, should also be vaccinated, particularly if they have not been exposed to hepatitis A, since the infection can cause liver failure in these patients.

The hepatitis A vaccine can be given along with immune globulin and other vaccines. Individuals should also receive immune globulin if they are exposed within 4 weeks of the vaccination. A combined vaccine against both hepatitis A and B is now available as well, for those at high risk for both these infections. People should get 3 doses of this vaccine, and the last dose should be given 6 months after the first dose. New 2010 immunization guidelines recommend that unvaccinated persons who anticipate contact with an overseas adoptee consider vaccination.

Side Effects. The vaccine is very safe and effective, although allergies can occur. The most common side effects reported are soreness at the injection site, headache, and general malaise.

Review Date: 10/12/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.