Medical Health Encyclopedia

The weakened or inactivated agent in the vaccine teaches the immune system to recognize the real, harmful substance and attack it when the person becomes exposed to the infection. The antibodies remain in the body, preventing future illness from the disease. This is called immunity.

Combination Vaccines. The American Academy of Pediatrics and American Academy of Family Physicians recommend that healthcare providers use, whenever possible, combination vaccines instead of individual components. Currently a child must have 20 injections in the first year of life for full recommended immunity. Combination shots containing vaccines for diphtheria, tetanus, and pertussis (DTaP), and for measles, mumps, and rubella (MMR) have been available for years. New combinations that cover up to five vaccinations are being developed and are proving to be safe and well tolerated in infants as young as two months. For example, one that combines DTaP, hepatitis B, and the polio vaccine (Pediarix) has been approved and should simplify the immunization process.

There is some concern that increasing use of combinations may reduce the potency of some of the vaccines within other combinations. Some parents are also worried about increased side effects. Studies, to date, however, are reporting that combinations are effective and safe.

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Passive Immunity. Another form of protection against disease is called passive immunity. This approach uses immune globulin, which are blood products containing antibodies. Immune globulin is generally used for people who cannot be vaccinated, when immediate protection is required, or to prevent severe complications of the disease. In some circumstances, passive immunity can interfere with active vaccinations, particularly live-virus vaccines, so, if possible, they should not be administered within weeks or even months of each other.