After a disaster recovery or planned migration, the recovery region becomes the protected region, but the VMs are not protected yet. If the original protected region is operational, you can reverse the direction of protection to protect the new primary region.
During the reprotect operation, after Site Recovery Manager reverses the direction of protection, it forces a synchronization of the storage from the new protected region to the new recovery region. Forcing data synchronization ensures that the recovery region has a current copy of the protected virtual machines running at the protection region. Recovery is possible immediately after the reprotect operation finishes.