Symantec Anti-Virus question

Not sure if I'm posting this in the right place or not, but here it goes....

Symantec End Point Anti-Virus... Lately i've been seeing alot of PC's on our network who are infected SEP finds the threat, tags it and kills it.  But is that enough? In a recent report (Top sources of attack) i saw over 15pc's with over 500 hits each... I believe the product is working as intended, but I suspect that it may be a better idea to just re-image these machines... I'm hoping someone else has seen something like this...

Any thoughts?

Thank you!