The most commonly used method of immunization is known as active immunization or vaccination. This involves the introduction into the body of a harmless form of an infectious organism that stimulates the body to produce antibodies against that organism. To provide immediate protection, a method called passive immunization is used. This introduces into the body “ready-made” antibodies extracted from people or animals who already have immunity to the infection.
Many vaccines are made from weakened forms of a disease-causing organism; these are known as live vaccines. Others use an inactive form or just a part of the organism, such as a protein. Protection may be lifelong, or booster shots may be needed.
Antibodies are formed in response to the organisms in the vaccine. A “memory” of these antibodies is retained by the immune system.
If the same organism invades the body at a later date, the immune system will recognize it and will rapidly produce antibodies to destroy it.
Immunity to an infectious organism can be achieved by the introduction of donated antibodies. This is needed if no active immunization is available or if rapid protection against an organism is vital, especially for people with weakened immune systems.
Antibodies taken from humans or animals with immunity to the infection are introduced into the body.
When exposed to the infectious organism, the antibodies immediately destroy it. They also provide short-term protection against future infection.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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