Numerous epidemiological cohort studies that have been conducted to prove or disprove that vaccines may cause autism hypothesis. But you cannot rely solely on epidemiological studies to test causality, because, at best, those kind of studies only have the ability to show a correlation. And correlation is simply not the same as causation.
According to Michael Green, JD, Michal Freedman, JD, MPH and Leon Gordis, MD, determining a “specific causation” between a virus or bacteria, for example, and a disease is “beyond the domain of the science of epidemiology.” “Even the most rigorous epidemiological studies suffer from a fundamental limitation,” says Georgia Ede, MD. “At best, they can show only association, not causation.”
I have cautioned against relying solely or to much on epidemiological cohort studies, which, for some odd reason, have become the be-all and end-all at the Centers for Disease Control and Prevention (CDC).
The fact is that epidemiology is a basic science, rather than an applied science. It is not equipped to prove anything. It is only capable of coming up with interesting data that might indicate a need for further research employing other kinds of studies, such as observational, biological mechanism, and animal studies, which can produce more conclusive results.