Veeam has published a migration utility to be used if you replaces your vCenter with another and moves all VM's to the new vCenter (with og without the ESXi hosts).
This Utility fixes the re-mappes theMoRef IOs of the VM's. This means that the backup will afterward continue and not create a new backup for the VM's.
The Utility does not do every thing you have to do some manual steps also.
It can be found here: https://www.veeam.com/kb2136
Notes: this utility is not supported by Veeam, so read the documentation carefully.