Since the start of widespread vaccinations in the United States, the numbers of cases of some formerly common childhood illnesses like measles and pertussis (whooping cough) have dropped by 95% or more. Immunizations have protected millions of children from potentially deadly diseases and saved thousands of lives. In fact, certain diseases crop up so rarely now that parents sometimes ask if vaccines are even necessary anymore.

This mistaken impression is just one common misconception about immunizations. The truth is, most vaccine-preventable diseases still exist in the world, even in the United States, although they occur rarely. The reality is that vaccinations still play a crucial role in keeping children healthy. Read more about immunizations and find out exactly what they do - and what they don't.

What Immunizations Do
Vaccines work by preparing your child's body to fight illness. Each immunization (given through a shot your child receives) contains either a dead or a weakened germ, or parts of it, that causes a particular disease. Your child's body practices fighting the disease by making antibodies that recognize specific parts of that germ. This permanent or long-standing response means that if your child is ever exposed to the actual disease, the antibodies are already in place and his body knows how to combat it, so he doesn't get sick. This is called immunity.

Facts and Myths
Unfortunately, misinformation about vaccines could make some parents decide not to immunize their child, putting him and others at a greater risk for illness. To better understand the benefits and risks of vaccines, here are a few common myths and the facts.

• The immunization will give my child the very disease the vaccine is supposed to prevent.
  This is by far parents' greatest fear about vaccines. However, it is impossible to get the disease from any vaccine made with dead (killed) bacteria or viruses or just part of the bacteria or virus. Only those immunizations made from weakened (attenuated) live viruses - like the chicken pox (varicella) or measles, mumps, and rubella (MMR) vaccine - could possibly make a child develop a mild form of the disease, but it is almost always much less severe than the illness that occurs when a person is infected with the disease-causing virus itself. The risk of disease from vaccination is extremely small.

  One live virus vaccine that is no longer used in the United States is the oral polio vaccine (OPV). The success of the polio vaccination program has made it possible to replace the live virus vaccine with a killed virus form known as the inactivated polio vaccine (IPV). This change has completely eliminated the possibility of polio disease being caused by immunization in the United States.

• If all the other children in school are immunized, there's no harm in not immunizing my child.
  It is true that a single child's chance of catching a disease is low if everyone else is immunized. Yet if one person thinks about skipping vaccines, chances are other people are thinking the same thing. And each child who is not immunized gives these highly contagious diseases one more chance to spread. This actually happened between 1989 and 1991 when an epidemic of measles broke out in the United States. Lapsing rates of immunization among preschoolers led to a sharp jump in the number of cases of measles, as well as the number of deaths and children with permanent brain damage. Similar outbreaks of pertussis (whooping cough) struck Japan and the United Kingdom in the 1970s after immunization rates declined.

  Although vaccination rates are fairly high in the United States, there is no reliable way of knowing if everyone your child comes into contact with has been vaccinated, particularly now that so many people travel to and from other countries. As the 1999 outbreak of encephalitis from West Nile virus in New York illustrated, a disease can hop halfway around the world very quickly because of international travel. The best way to protect your child is through immunization.