Vaccination

Definition

Vaccination is the use of vaccines to produce immunity to specific diseases.

Purpose

Many diseases that once caused widespread illness, disability, and death now can be prevented through the use of vaccines. Vaccines are medicines that contain weakened or dead bacteria, viruses, or pollen antigens. When a person takes a vaccine, his or her immune system responds by producing antibodies—substances that weaken or destroy disease-causing organisms. When the person is later exposed to live bacteria or viruses of the same kind that were in the vaccine, the antibodies prevent those organisms from making the person sick. In other words, the person becomes immune to the disease the organisms normally cause. The process of building up immunity by taking a vaccine is called immunization.

Vaccines are used in several ways. Some, such as the rabies vaccine, are given only when a person is likely to have been exposed to the virus that causes the disease, such as through a dog bite, for example. Others are given to travelers planning to visit countries where certain diseases are common. Vaccines such as the influenza vaccine, or "flu shot," are given mainly to specific groups of people—older adults and others whose health is at high risk if they develop influenza or its complications. Then, there are vaccines that are given to almost everyone, such as the one that prevents diphtheria.

Children routinely have a series of vaccinations that begin at birth. The American Academy of Pediatrics recommends that children be fully immunized before the age of two years in order for them to be protected during their most vulnerable period. Given according to a specific schedule that is issued every year by the Department of Health, these vaccinations protect against hepatitis B, diphtheria, tetanus, pertussis, measles, mumps, rubella, varicella (chickenpox), polio, and Hemophilus influenza type B (Hi B). This series of vaccinations is recommended by the American Academy of Family Physicians, the American Academy of Pediatrics, and the Centers for Disease Control and Prevention and is required in all states before children can enter school. All states will make exceptions for children who have medical conditions such as cancer that prevent them from having vaccinations, and some states also will make exceptions for children whose parents object for religious or other reasons.

Vaccines are also available for preventing anthrax, cholera, hepatitis A, Japanese encephalitis, meningococcal meningitis, plague, pneumococcal infection, tuberculosis, typhoid fever, and yellow fever.

Some vaccines are combined in one injection, such as the measles-mumps-rubella (MMR) or diphtheria-pertussis-tetanus (DPT) combinations.