It is easy to class out what could have an effect when it is something easily as monitored and controlled like vaccinations. Changes in vaccination rates have had no influence over autism diagnosis rates. So while common sense tells you therefore the two aren't linked due to the lack of correlation there have also been comprehensive statistical studies to back the hypothesis that there is no link.
Why we don't have a solid answer to a cause of autism is because it is likely to be a combination of factors, both genetic and environmental (and likely not a single combination of those). There are plenty of other modern environmental factors that are suspects and but the alt-medicine lobby seems to be leveraging this disproven hypothesis for they own ends. Alt-medicine is big business, for example I know a couple of people making "fuck you" money doing it.
I agree that the human element is always a factor in studies which is why scientists go to great lengths to remove them such as double blind studies for example where both the tester and subject don't know which group the subject belongs to (test or control).
Why we don't have a solid answer to a cause of autism is because it is likely to be a combination of factors, both genetic and environmental (and likely not a single combination of those). There are plenty of other modern environmental factors that are suspects and but the alt-medicine lobby seems to be leveraging this disproven hypothesis for they own ends. Alt-medicine is big business, for example I know a couple of people making "fuck you" money doing it.
I agree that the human element is always a factor in studies which is why scientists go to great lengths to remove them such as double blind studies for example where both the tester and subject don't know which group the subject belongs to (test or control).