Can there be mercury in a 9 month old baby's flu shot vaccination?

Yes. See dr pizzo's response. But keep in mind that the type of mercury ( and there are safe and not safe types) in the shot has been demonstrated in many, many research studies to not have or cause any serious side effects in babies whereas the influenza infection can be deadly, causing unfortunately several thousands deaths in children per year. Do not be afraid. Get the shot!
Mercury in flu shot. It depends on how the vaccine is made and put up. 80% per cent of the flu shots have mercury (thimerosol) in them. 20% are mercury free and usually put up in single dose vials as oppossed to multiple dose vials. You can request a mercury (thimerosol) free vaccine from your pediatrician or other doctors. The regular flu vaccine has 25 micrograms of thimerosol per dose and they give 2 doses.