Babies are born with protection against some diseases because their mothers pass antibodies (proteins made by the body to fight disease) to them before birth. Breastfed babies continue to get more antibodies in breast milk. But in both cases, the protection is temporary.

Immunization (vaccination) is a way to create immunity to (protection from) some diseases. This is done by using small amounts of a killed or weakened germ that causes the disease.

Germs can be viruses (such as the measles virus) or bacteria (such as pneumococcus). Vaccines stimulate the immune system to react as if there were a real infection. It fends off the "infection" and remembers the germ. Then, it can fight the germ if it enters the body later.

What Are the Types of Vaccines?

There are a few different types of vaccines. They include:

• Attenuated (weakened) live viruses are used in some vaccines such as in the measles, mumps, and rubella (MMR) vaccine.
• Killed (inactivated) viruses or bacteria are used in some vaccines, such as in IPV.
• Toxoid vaccines contain an inactivated toxin produced by the bacterium. For example, the diphtheria and tetanus vaccines are toxoid vaccines.
• Conjugate vaccines (such as Hib) contain parts of bacteria combined with proteins.

The American Academy of Pediatrics (AAP) recommends that kids get combination vaccines (rather than single vaccines) whenever possible. Many vaccines are offered in combination to help reduce the number of shots a child receives.