When you introduce a microbe (a bacterium or virus) into the bloodstream, that
amazing network of cells that we call the IMMUNE SYSTEM searches them out and
tries to destroy them. This is because it has the ability to tell the difference
between something foreign, like a bacteria, and cells that belong to our bodies.
Many microbes are so tricky that it is really hard for our bodies to fight the
infection....and we get sick. The virus that causes the common cold is one of
the trickiest! Why? For many bacteria and
viruses, if we are exposed to them often enough, our body builds up an IMMUNITY.
This means that our immune system has been trained so well to fight off a disease,
that the bacteria are killed off before they can make us sick. By injecting
someone with either a "little part" of a microbe or a microbe that has been
heat killed (vaccination), we are training the immune system to be an expert
at recognizing and killing off that invader.
If levels of vaccination decrease, many of the (currently) more rare diseases can come back as serious human threats...since many viruses and bacteria have the ability to "hide out" in other animals and be passed between these animals and humans.
A note about adult vaccination....even if you were vaccinated as a child, it is often recommended to update certain vaccinations (ESPECIALLY if you will be doing any international travelling). See this CDC site for more info. In addition, it is a good idea to check CDC recommendations when travelling to more exotic places. It may be suggested that you get vaccinated against certain diseases (such as yellow fever or hepatitis) or that you take anti-malaria drugs to prevent getting the disease. Some vaccinations require 3 shots over a 6 month period, so try to think ahead!
Information on Vaccine
Shortages (United States 2004), in particular, 3rd and 4th dose of Pneumococcus
(Prevnar) vaccine may need to be delayed. See here.
Adverse events associated with 17D-derived Yellow Fever Vaccination (United States, 2001-2002)
Danish study finds no link between thimerosal and autism
March 2004 - 10 of the 13 original authors of a 1998 study linking the MMR vaccine to a type of autism have retracted their conclusions
U.S. Institute Of Medicine finds no evidence linking MMR vaccine and thimerosal to autism - Infectious Diseases in Children article
Can a vaccine actually cause the disease it is meant to prevent?
Evaluating Vaccine Safety Information
If you decide NOT to have your child vaccinated...
While I personally believe in having my children vaccinated, I realize that some parents have very strong personal or religious reasons for not wanting their children vaccinated. Additionally, in rare instances, a parent or other family member may have had a severe reaction to a particular vaccine and may be counselled against having their child receive this vaccine (as allergies and severe reactions may be hereditary). In this case, it is strongly recommended to:
Harvard Med School Parent Issues includes some articles on vaccination
Excellent primer on vaccines from Children's Hospital of Philadelphia
United Kingdom NHS immunization homepage
Excellent article on the "Is vaccination safe" debate (pdf file)
6 common misconceptions about vaccination
Funny and comprehensive article about vaccination from a pediatrician's perspective