 Today, some anti-vaccine activists are using the same tactics against the Miesel's Moms and Rubella or MMR series that was used in the past against DTP. The claim is that MMR, given together rather than individually, carries some risk of causing autism in young children. In the usual fashion, very bad science has been used to show a weak correlation. The media, and in this case the celebrities Jenny McCarthy and now Jim Carrey, are reacting on an emotional level and attempting to justify their beliefs with evidence. They want autism to be someone else's fault rather than a random and complex etiology with poorly defined symptoms. Most of the science around this has been thoroughly discredited, although rarely with the same media coverage. The most famous case is the 1998 paper in the journal The Lancet. Andrew Wakefield, the primary author, was later found to be in the employ of the trial lawyers who were suing the vaccine manufacturers. Further investigation found that he had substantially interfered with and manipulated the study to create the link between MMR and autism. Ten of the twelve authors of the paper have retracted it. The publicity surrounding the Lancet paper led to an investigation of the link between autism and scheduled vaccination, by the Centers for Disease Control and Prevention, the Institute of Medicine of the National Academy of Sciences, the UK National Health Services, and the Cochrane Library. All found no link between the vaccine and autism. Perhaps the best paper I have seen on the top because a 1998 paper in the New England Journal of Medicine showing the rates of autism in the two years before and the two years after the introduction of the MMR vaccine into Sweden. This was a well matched population with the minimum of confounding effects and well controlled for important factors. The authors had no interest on either side of the debate. They found no correlation between MMR and autism in the population of Sweden. The results are never as exciting or emotional and have been ignored by the anti-vaxxers as tainted or part of a vast conspiracy by the vaccine manufacturers. But even those studies that show a weak correlation in a small population would fail those three factors that I have identified so far. They would not have a repeatable mechanism and they would not be able to statistically predict autism rates. I want to examine several of their arguments from the website Generation Rescue. Point one, in 1983 autism rates were one in 10,000 and there were 11 vaccines in the pediatric schedule. Today there are 36 pediatric vaccines and autism rates are reported as high as one in 80 in local school districts in Oregon and New Jersey. Now does that remind you of the Mexican lemons and traffic fatalities? Because it's pure correlation. No causation is implied. If we're going to speculate the more likely explanation for the increase in autism rates since 1983 is an increase in diagnosis. How many other things didn't exist in 1983 but do today? Perhaps Netscape causes autism or perhaps Parachute Pants suppress autism. Each of these ideas has just as much correlative merit. Point two, the US has the most bloated vaccine schedule and also the highest autism rate when compared to other countries. Again, pure correlation. We also have a very different culture, geography, diet, medical system and educational and economic structure than those other countries. Could it be that the high ratio of psychologists capable of diagnosing and sometimes even overdiagnosing autism is responsible? Point three, several scientific studies have shown that early vaccinations associated with other diseases such as type 1 diabetes and asthma. That may be true. The data is very weak and the studies are characterized by one important confounding factor. The populations with the lowest rates of vaccination tend to be either very low income or very high income thanks to this movement. An unvaccinated child therefore does not represent the norm and despite some effort on the part of researchers it's very hard to find groups of patients called cohorts of equal size and exactly equal in every other respect. In my home state of Texas, the chance that a child of an undocumented immigrant being fully vaccinated is very low. These same families tend not to seek expensive autism evaluations. A high or middle income family that follows the vaccination schedule very closely are also more likely to seek autism evaluation. So the reporting rates may be much higher. Between the two groups we can also expect large differences in diet, toxin exposures, regular medical care and home environment especially smoking in the home. When we try to match these factors the correlations become much weaker or disappear. Point four, autism is often diagnosed within a few months of the MMR vaccine being administered at 12 or 18 months. While this may be true it is again a correlative relationship only. Autism is first diagnosable at about the same time as the second round of MMR vaccine 18 months. Point five, vaccines contain high levels of either mercury or aluminum which we know are neurotoxins. This may be true and repeated exposures to high levels of mercury and aluminum can lead to neurotoxicity. Thimerazole which is an organic form of mercury is no longer used in the US in routine vaccinations. It was used as a preservative because it's safe as an injectable, does not affect the vaccine agents and is stable for long times. The mercury has a blood half-life of 3.7 days and up to 14 days in the brain. Now you have to remember that we are talking about here is a maximum one time dose in the worst case scenario of 1000 micrograms or 1 milligram of aluminum salt. Compare that to the 15 milligrams of zinc I take every day in my multivitamin or the 2 milligrams of copper or the 2 milligrams of manganese. One milligram is a very low one time dose and it hasn't been shown that toxicity is a linear, non-threshold model, something I will be talking about in a future video. So in conclusion, while there is some weak correlative evidence, positive causation has never been established. Even if we view this as a risk assessment with the potential correlative risk of autism being acknowledged, the benefit of millions of children not dying from measles, mumps and rubella outweighs the risk of hundreds of additional children developing autism. A final note, the 1918 pandemic influenza, which is believed to have originated in Kansas in the wake of World War I, is estimated to have infected one out of every three people in the world and to have killed almost 100 million people, roughly 20% of all who were infected. I hope nothing like that ever happens again. But our best weapon against such pandemic disease is vaccination. Get your seasonal flu shot, then get the H1N1 shot as well. You're protecting yourself and everyone you love. Thanks for watching.