Observational Vs. Experimental Studies for the Autism Vaccine Question
Posted Aug 16 2009 12:00am
By Catherine Tamaro
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.