The chemicals in the vaccines can cause deadly reactions, and there are some who claim (I say claim because there are no studies other than parental claims) that after getting vaccinations their child developed autism. I vaccinated my oldest and am vaccinating my baby. Neither have really had any reactions to any vaccines though I am going to talk to my kid's doctor before the next round for my baby because the last two times he got shots he ended up with a huge lump under the skin from one of the shots that lasted a few weeks.
Both of my children are fully vaccinated. My oldest used to get a fever when he was younger, he's 7 now, but that is all. My four month old doesn't even get that after vaccinations. We feel that the protection (even though it's not a guarantee) of the vaccination far outweighs the negative things some people have to say about vaccines. We've done our research and find nothing wrong with the ingredients. Personally, I'd rather try to protect my kids from these diseases then just hope they never come in contact with them. Some choose not to do it for various reasons, to each their own.
I don't vaccinate because I feel it is unessessary to put the harmful chemicals in vaccines into my child's body... Also a child's immune system doesnt need to be interfered with especially under the age of 2. The human body was made to heal itself vaccines only distract and confuse the immune system.