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• Immunization Terms

Immunization Related Terms

- H -

• Haemophilus Influenza Type B (HIB)

A bacterial infection that may result in severe respiratory infections, including pneumonia, and other diseases such as meningitis.



• Hepatitis A

A minor viral disease, that usually does not persist in the blood; transmitted through ingestion of contaminated food or water.



• Hepatitis B

A viral disease transmitted by infected blood or blood products, or thorugh unprotected sex with someone who is infected.



• Hepatitis C

is a liver disease caused by the Hepatitis C virus (HCV), which is found in the blood of persons who have the disease. HCV is spread by contact with the blood of an infected person.



• Hepatitis D

is a defective virus that needs the hepatitis B virus to exist. Hepatitis D virus (HDV) is found in the blood of persons infected with the virus.



• Hepatitis E

is a virus (HEV) transmitted in much the same way as hepatitis A virus. Hepatitis E, however, does not often occur in the United States.



• Herd Immunity

See Community immunity.



• Herpes Zoster

A disease characterized by painful skin lesions that occur mainly on the trunk (back and stomach) of the body but which can also develop on the face and in the mouth. Complications include headache, vomiting, fever and meningitis. Recovery may take up to 5 weeks. Herpes Zoster is caused by the same virus that is responsible for chickenpox. Most people are exposed to this virus during childhood. After the primary infection (chickenpox), the virus becomes dormant, or inactivated. In some people the virus reactivates years, or even decades, later and causes herpes zoster. Also known as the shingles.



• Hives

The eruption of red marks on the skin that are usually accompanied by itching. This condition can be caused by an allergy (e.g. to food or drugs), stress, infection or physical agents (e.g. heat or cold). Also known as uticaria.



• Hypersensitivity

A condition in which the body has an exaggerated response to a substance (e.g. food or drug). Also known as an allergy.



• Hyposensitivity

A condition in which the body has a weakened or delayed reaction to a substance.