The argument of “bad vaccines” is a very popular one. However, scientifically seen this arguments is flawed in many aspects.  First of all many of the examples used in arguments suggesting vaccination is dangerous and therefore should not be used, is very old. Many refer to examples from the 60s or 70s, which in medicine is highly flawed as science every few years significantly advances, improves the level of knowledge and reduces possible side effects. And even though many believe in the damages caused by vaccines retrospective studies disprove this point:  1. Autism  Scientists at Columbia University Mailman School of Public Health's Center for Infection and Immunity and researchers at the Centers for Disease Control and Prevention, Massachusetts General Hospital, and Trinity College Dublin, evaluated bowel tissues from 25 children with autism and GI disturbances and 13 children with GI disturbances alone (controls) by real-time reverse transcription (RT)-PCR for the presence of measles virus RNA. Samples were analyzed in three laboratories blinded to diagnosis, including one wherein the original findings suggesting a link between measles virus and autism had been reported. [1]  "Our results are inconsistent with a causal role for MMR vaccine as a trigger or exacerbate of either GI difficulties or autism," states Mady Hornig, associate professor of Epidemiology and director of translational research in the Center for Infection and Immunity in the Mailman School, and co-corresponding author of the study. "The work reported here eliminates the remaining support for the hypothesis that autism with GI complaints is related to MMR vaccine exposure. We found no relationship between the timing of MMR vaccine and the onset of either GI complaints or autism. [2]  Many parents came to believe that vaccines caused their children's autism because the symptoms of autism appeared after the child received a vaccination. On a psychological level, that assumption and connection makes sense; but on a logical level, it is a clear and common fallacy with a fancy Latin name: post hoc ergo propter hoc ("after this, therefore because of it"). They just need someone to blame for the disease of their child. [3]  2. Allergies and vaccines  A recent (2011) study of a German Health Institute concludes that in comparing the occurrence of infections and allergies in vaccinated and unvaccinated children and adolescents. These include bronchitis, eczema, colds, and gastrointestinal infection. The only difference they found is that unvaccinated children and adolescents differ from their vaccinated peers merely in terms of the frequency of vaccine preventable diseases. These include pertussis, mumps, or measles. As expected, the risk of contracting these diseases is substantially lower in vaccinated children and adolescents. [4]  [1] Science Daily, No connection between Measels, Mumps, Rubella (MMR) Vaccine and Autism, Study suggests 09/05/2008 http ://www.sciencedaily.com/releases/2008/09/080904145218.htm  [2] Ibid.  [3] Benjamin Radford, Autism and sciences: Why bad Logic Trumps Science, 09/05/2008   [4] Deutsches Aerzteblatt International (2011, March 7). Vaccinated children not at higher risk of infections or allergic diseases, study suggests. ScienceDaily.  , accessed May 28, 2011