Backup Exec 2012 vs backing up VMware ESX 5.1 host and not the VMs themselves

Hello,

We have 3 VMware ESX 5.1 hosts that contains multiple Windows VMs.

Is there a way we can backup these hosts ?    We already backup all the VMs but I just noticed that we do not backup the hosts themselves. (the ESX hosts).

Let me know if we should back them up or not and if not, why.

Do we need a specific agent for that ?     Looks to be a linux of something like that,  that is driving the ESX hosts.

I know there is a VMware agent but as far as I know,  It is for backing-up VMs or something like that.  (I've created another post for that too).

thanks for any help.