After reading Katie Wright’s summary of the August 3 Senate Committee on Appropriations’ hearing on autism (HERE), I would like to comment on Dr. Insel’s testimony to Senator Harkin on why a study comparing vaccinated vs. unvaccinated children has not been done to date. Dr. Insel claimed that such a study would be “unethical” because, as he apparently envisions it, the study would entail dividing a large cohort of newborns into two groups, vaccinating one cohort but not the other through age two, and then comparing outcomes. This is just a bit disingenuous and I would like to explain why.
Research studies are divided into two categories, observational studies and experimental studies. An observational study observes individuals and measures variables of interest but does not attempt to influence the responses. (The “epidemiological” studies to which Dr. Insel refers are actually observational studies.) An experimental study, on the other hand, deliberately imposes some treatment on individuals in order to observe their responses; the purpose of an experiment is to study whether the treatment causes a change in the response.
All studies done to date investigating a correlation between vaccinations and autism have been observational studies, but no observational study has been done comparing the prevalence of autism diagnoses in a vaccinated human population compared to an unvaccinated human population. When Dan Olmsted points out that he has identified large populations of unvaccinated children in the United States and asks why a study has not been done on them, he is actually asking why an observational study has not been done. When Senator Harkin asks Dr. Insel why a study has not been done on vaccinated vs. unvaccinated American children, he too is actually asking why an observational study has not been done to date. Dr. Insel, however, chooses to respond by saying that an experimental study would be required in order to resolve the issue. Given that it is unlikely Dr. Insel rose to the top of the NIMH without learning the distinction between observational and experimental studies, we can only assume that he knows quite well what is being asked of him and is actually responding to the question “Why hasn’t a study been done” with a response of “Because we’re no interested in doing it” – with a little bit of technical bluff to remind the nonscientists at the hearing that they don’t understand “science.”
I would like to point out the epidemiological similarity between smoking/lung cancer and vaccines/autism. Smoking has been proven to cause lung cancer, yet not a single experimental study on humans was ever done – all of the human studies proving that smoking causes lung cancer were observational. The experimental studies were performed on research animals only. Attached at the end of this letter is a lesson taken verbatim from an introductory course in college statistics describing how the connection between smoking and lung cancer was made.
Thus what Dr. Insel doesn’t say is that the NIH has chosen to forego all experimental animal studies on vaccination effects and all observational studies comparing populations of vaccinated vs. unvaccinated human children, under the guise that any study demonstrating a link between vaccines and children necessarily involves experimenting on children. From a statistician’s perspective, however, these kinds of studies could be performed easily, with no need whatsoever for experiments to be performed on children. The staff at NIH clearly have the expertise, the resources, and the funding to mount such studies – if they wanted to do them. But as Dr. Insel insinuates (but doesn’t quite come out and say), the fact is, they don’t want to. His testimony is misleading and disingenuous and I sincerely hope that the next time he (or anyone else from NIH) is questioned about why the NIH hasn’t commissioned any studies on the effects of vaccination, he is pushed to give a more responsive answer.
Supporting Causation Without Experimentation
1. Strong Association
2. Association consistent across studies
3. Higher doses associated with stronger responses
4. Alleged cause precedes the effect in time
5. Alleged cause is plausible
More criteria met → Stronger case for causation
Smoking and lung cancer
Without ever experimenting on human subjects, U.S. Surgeons General have long stated that smoking causes lung cancer. This statement can be made because the relationship meets the criteria for establishing causation.
1. Very strong measures of association between smoking and lung cancer found in observational studies.
2. Multiple studies show same outcome across time and geographic boundaries.
3. Heavy smoking has greater risk than light smoking.
4. Smoking predates contracting lung cancer.
5. Connection between tars and lung cancer has been proven in animal experiments making cause plausible.
Source: The Basic Practice of Statistics, Fourth Edition, pub. 2007, by David S. Moore. W.H. Freeman & Company, New York.
Catherine Tamaro has two sons, one born in 1996 and diagnosed with ASD at 3-1/2, the other born in 1998 and NT with colitis. She has a degree in mechanical engineering and lives in WA. She moderates the Vitamin K Yahoo list.
TrackBack URL for this entry:
Listed below are links to weblogs that reference Observational Vs. Experimental Studies for the Autism Vaccine Question: