A special US court, often referred to as the "vaccine court," was convened to test claims of a causal connection between the administering of a vaccination (generally the Measles, Mumps, Rubella, or MMR vaccine) and the onset soon-after of paediatric autism.
The court stipulated (on page 22, here) that any successful petition to the courts must present three things successfully.
(1) "a medical theory" that causally connects the vaccinations and the child's autism;
(2) "a logical sequence of cause and effect" that shows that the child's vaccinations were the "reason" for the injury;
(3) evidence of "a proximate temporal relationship" between vaccination and injury.
The court tested two possible theories.
The first theory being that the vaccination itself was the cause and the second being that the mercury-containing compound Thimerosal, used as a preservative.
Neither theory stood up to the scrutiny of experts or the court officials.
According to the published decision "The undersigned [one of the three 'special masters' hearing the evidence] observes that while petitioners' experts were qualified, they lacked the specialized qualifications that distinguished respondent's experts.
"The focus of the extensive research conducted by respondent's witnesses coupled with the significant clinical experiences of respondent's witnesses provided well-informed guidance concerning the various aspects of petitioners' theory of vaccine-related causation.
"The testimony of respondent's witnesses made clear that petitioners' presented theory of causation was biologically implausible and scientifically unsupported. Petitioners' experts openly conceded the limitations of their expertise during cross-examination, and the testimony given by petitioners' experts showed both internal inconsistencies and notable external inconsistencies with established scientific principles.
"These inconsistencies in the testimony of petitioners' experts-that were exposed, in part, through the testimony of respondents' experts-diminished the persuasiveness of the opinions that petitioners' experts offered, and, in the view of the undersigned, called into question the soundness of the positions that they offered."
In commenting on the mercury claim, Patricia Campbell-Smith, the master in the Mead case (quoted here) noted that vaccine opponents "have not shown either that certain children are genetically hypersusceptible to mercury or that certain children are predisposed to have difficulty excreting mercury. "She also echoed a contention by vaccine defenders that a shot is safer than a tuna sandwich. "A normal fish-eating diet by pregnant mothers" is more likely to deposit mercury in the brain than vaccines are."
One of the Internet's best-known medical sites, WebMD has an article on the topic which notes, rather tellingly, that "experts studied whether the MMR vaccine could cause autism. To do that, they looked for clues among kids who did and didn't get the vaccine.
"Since that initial finding, 14 studies including millions of children in several countries consistently show no significant difference in autism rates between children who got the MMR vaccine those who didn't.
"The bottom line: It's very unlikely that the MMR causes autism."
The New York Times also commented on the ruling, exposing one of the many motivators for parents to blame vaccines for Autism: "The master in the Dwyer case wrote that many parents 'relied upon practitioners and researchers who peddled hope, not opinions grounded in science and medicine.' "
It has been a long and difficult path for rational science to recover from the damage done by Dr Andrew Wakefield's original research paper. However, the paper is noew entirely discredited and extensive work has been done to expose those supporting the connection as seriously misinformed (to be remarkably kind).
Even with this decision, Dr. Offit (director of the Vaccine Education Center at Children's Hospital of Philadelphia and the inventor of a rotavirus vaccine from which he receives royalties) said, "it's very hard to unscare people after you've scared them."
Of course, nothing here will change the fact that a number of children have developed autism within a short time of receiving a vaccine. However, the decision is clear - the vaccine isn't guilty; in fact a number of researchers have pointed out that the vaccine is generally administered to children when they are at the same age that symptoms of autism frequently appear.