Skepticblog

Facebook is like a graveyard in a zombie movie, where old news items rise from the dead to have a second life. I am often asked about news items that are burning up Facebook, only to find that they are years old, but never-the-less they have to be addressed all over again. ]

One such item (actually a few items) is a 2012 news report about the Italian courts awarding money to the Bocca family a large reward because it concluded their 9-year-old son acquired autism from the MMR vaccine.

History here is a useful guide. The courts have historically often been out-of-step with the science, tending to err on the side of awarding compensation for possible harm. For example, until about the 1920s it was thought that physical trauma could cause cancer. Animal studies and epidemiological evidence, however, showed that there was no causal connection. Recall bias and increased surveillance were likely the cause of the apparent association.

However, this did not stop the courts from awarding damages to individuals based upon the notion that minor trauma caused their cancer – even decades after the scientific community rejected this notion. A legal paper on this topic demonstrates the difference in approach:

The author feels that the legal concept of causation is best satisfied by the sequence of events test, which results in a shifting of the burden of proof to the defendant.

In other words – if the cancer happened after the trauma it is reasonable for legal purposes to assume that the trauma caused the cancer (the post hoc ergo propter hoc logical fallacy), and then to shift the burden of proof to the defendant so that they now have to prove that the trauma did not cause the cancer.

Another example is that of silicone breast implants and autoimmune disease. A series of class-action suits were brought against Dow Chemical and Dow Corning  for cases of lupus and other autoimmune disease  alleged caused by ruptured implants. Many multi-million dollar judgments were made against the companies, and Dow Corning filed for bankruptcy to protect itself against the slew of suits.

This was not based on any solid scientific evidence that breast implants actually caused autoimmune disease, but rather on the difficulty in ruling out that it did. Even completely negative studies do not rule out a connection – the more data we have, rather, the smaller a possible risk can be. We can never, however, rule out a tiny risk or a rare reaction. This, of course, opens the door for legal cases claiming to be that one rare case.

The most recent review of the epidemiological evidence I can find is from 2004, and they conclude that there is no evidence linking silicone breast implants and autoimmune disease.

These historical cases, and others, demonstrate that the legal standard for concluding a causal connection to harm is different than the scientific standard – it is lower, and errs on the side of concluding that harm did occur. This is deliberate, the philosophy being that the courts do not want possible victims to go uncompensated just because the science is unsettled. However, this keeps the door perpetually open for claims of rare cases, because scientific data will never be sufficient to rule out rare causal events.

For antivaccinationists who do not want to give up on their claim that vaccines cause autism, court rulings provide the occasional propaganda boon. They use the courts as a proxy because they have lost their case in the scientific arena.

I have discussed the evidence for vaccines and autism many times, and a fairly thorough reference of that evidence can be found here. The MMR vaccine is not causally linked to autism, and neither is thimerosal or vaccines in general.

Ironically, when the vaccine court in the US was asked to directly address this question they concluded that MMR and thimerosal, separately or in combination, do not cause autism. However, in individual cases in which neurological injury is alleged the courts do sometimes conclude that “compensation is appropriate.” The word choice is also deliberate – they are not making scientific conclusions, only saying that by the rules of the court the family should be compensated, acknowledging that those rules set the bar much lower than scientific consensus.

Also, in many of these cases the courts are not finding that the vaccines caused autism, but neurological injury that may have some autistic features. This is not a quibble – the idea is that vaccines can rarely cause encephalitis – swelling of the brain – which can cause brain damage. When encephalitis occurs after a vaccine, that is a table injury, meaning that the mere association is sufficient to justify compensation (in line with the legal standard recommended above). Having encephalitis that causes brain damage which produces some features that resemble autism is not the same thing as having autism. It is therefore not legitimate to conclude from these cases that vaccines cause autism.

This doesn’t stop the antivaccinationists from doing just that.

Conclusion

The scientific data is largely in – to a high degree of confidence we can conclude that vaccines do not cause autism. The data can never demonstrate that the risk is zero, but if it does exist it is very small. It is tiny enough that the benefits of getting vaccinated vastly outweigh the possible risks.

The courts have the burden of deciding in individual cases whether a potential victim should be compensated. They have to deal with often conflicting or inconclusive science, or the residue of rare but possible risk that can never be eliminated. The courts tend to err on the side of victims. Such decisions, however, do not trump the scientific evidence. They are grist, however, for the antivaccine propaganda mill.