This sensitive subject spreads world wide. As far as I know, this problem exploded after The Lancer's publication (British health magazine) in 1998.
13 medics created a false study "Ileal-lymphoid-nodular hyperplasia, non-specific colitis and pervasive developmental disorder in children" including only 12 children (it's mandatory for such studies to involve at least 1000-2000 volunteers), besides, some of them were related to each other (brother-sister). The study claims that there's a connection between autism, inflammatory bowel disease and MMR vaccines. Also those doctors withdrew their statement some of them losing their practice rights, but this part was just too hard for media to fix.
Shortly, vaccination is the administration of antigens (small fractions of microbes) that only stimulates your body to produce antibodies (against those specific antigens) that remain into your body to fight a (very) possible infection that otherwise would cause disease.
Of course, just like everything on this planet, it may have adverse reactions, there may be some isolated cases of death, but focusing on the advantages, life expectancy have raised significantly in the last century due, between other progress associated factors, to vaccines.
I will come up with an article with more details.
Take care! :)