Technically no - but yes you should!
Basically, the reason for yes is that it is simply best practice - any form of malware could infect your machine inbetween updates (e.g. 0-day outbreak) and be on your machine. Scanning your computer will check your hard drive against the latest signatures and simply ensure that you are protected.
However, I also said technically no - A virus cannot do any damage simply by being there, it needs to be executed. But, you would also need to understand how it got there in the first place.
You could've been infected by a 0-day type exploit in Acrobat, Flash, Java or other which executed - not being detected by the scanner and then left a few files, technically harmless but still part of that virus - or it could leave something such as a scheduled task to be executed at a later date.
However, when you do update your scanner, it should be able to detect any active processes that previously snuck past it if it is still running and also detect any part of the malware (e.g. if it left a scheduled task or a .dll loaded in to Windows). But, if it did manage to get on your system in the first place, technically it could also have installed a rootkit or other bypass mechanisms.
Anyway - it most likely will come up with nothing (other than possible tracking cookies or other harmless stuff depending on the scanner) but there is no harm in scanning - personally, I would leave it as a scheduled task.