I am sure you have heard at some point, probably from the mouth of some celebrity (Jim Carrey, Jenny McCarthy, Bill Maher, etc.) that they believe vaccines can cause autism. I am not going to go on at length about this (I will provide links you can go to for that below). I will just say a few things. First, there is no evidence to suggest that vaccines cause autism. The only reason anyone ever connected the two is because infants usually get vaccines around 10-12 months of age, whereas autism usually gets diagnosed between 12 and 24 months because this is when the child should start developing more social and communicative behaviors (like learning to talk). Because the one so closely follows the other, people have assumed a connection that simply isn't there, just a coincidence of physical development (an immune system developed enough to get vaccines) and brain development (one developed well enough to start talking). Second, the scapegoat here, or what tends to get blamed most often is the mercury found in a preservative called thimerosal which used to be used in vaccines. Almost all vaccines are now thimerosal-free, or as close to it as possible (except for some of the influenza vaccines), yet people still claim that vaccines are causing autism (despite all the evidence that shows that vaccines with thimerosal never caused autism, see below). Third, some people site the fact that the incidence of autism has increased over the past several decades as evidence of a link since this coincides with increases in both the numbers of children getting vaccines, and the use of thimerosal in those vaccines (since about the 1970s). Without getting into the whole correlation is not cause argument again (especially since autism can even be correlated to how much it rains) studies have since come out that directly compared the incidence of autism before and after thimerosal was removed from vaccines and showed no differences in the amount of kids being diagnosed with autism (some of the reports are summarized here). It is also important to note another correlation that coincides with the increased incidence and that is increased awareness and education about autism spectrum disorders (which as a group has grown to include many different disorders in addition to classically defined autism). This increased awareness has led to many doctors being able to catch or diagnose the disease in more children early on, which in turn would lead to what looks like an increased incidence, but may just be the result of better diagnosticians. Finally, it is understandable that parents of autistic children would want to blame someone or something for their child's disorder. The reasons for this are many (some even financial like in this case), but mostly because, as a parent of an autistic child, you can often feel helpless to do anything, and frustrated on many levels. Latching on to a cause (political, if not medical) gives some sense of control and a feeling of being able to work to fix the problem, or prevent it in the future. This is only natural, and understandable, and these parents do have my sympathy. HOWEVER, vaccines are CRITICAL to public health, and to individual health. Very few drugs, if any, have ever had the successes that we see with vaccines (like the almost complete eradication of polio and smallpox for example, which are not completely eradicated because there are still populations of people who do not get vaccinated). Childhood vaccines are unbelievably important, and will, in many cases, prevent not only several diseases, but DEATH. For example measles kills hundreds of thousands of children in the rest of the world, but not in the US because most kids are vaccinated, and, thanks to a widespread vaccination program in Asia, the number of deaths resulting from measles outside of the US has dropped nearly 80% since 2000. If you are a parent, don't let unreasoned and unsubstantiated fears prevent you from keeping your child ALIVE and healthy.
That's pretty much all I have to say on the subject, but, like I said, here are some links for you to check out on your own from some pretty reputable sources, like the FDA, and the American Medical Association (with others in there for good measure).