Autism and MMR Vaccine
A Call for Placebo-Controlled StudiesPeople claim that epidemiological evidence, such as the population-based studies that have already been performed, is not able to detect the rare cases of vaccine-linked autism, although this argument itself reinforces the evidence that the MMR vaccine is not causing an autism epidemic. Some parents and healthcare providers -- most notably the popular Dr. Bob Sears -- have suggested that this issue cannot be fully resolved until placebo-controlled studies have been performed.
In order to do this, a large group of children would be randomly given either the MMR vaccine or a placebo vaccine. In a double-blind trial, neither the healthcare providers nor the children (or their parents) would know who received the real vaccine and who received the placebo. This prevents preconceived notions or the "placebo effect" from interfering with the results.
While this kind of study would certainly provide useful information, it might be considered unethical -- after all, it would be leaving many children unprotected from potential measles, mumps, or rubella infections. In addition, even if large, carefully designed placebo-controlled studies were performed and suggested no link between autism and the MMR vaccine, this would probably not change the minds of many critics of the vaccination.