According to forum thread over at https://forum.vyos.io/t/add-intel-microcode-to-included-packages/6223 the microcode updates packages for intel and amd64 cpus are still not included in VyOS.
These should be included for security purposes:
https://packages.debian.org/bookworm/admin/intel-microcode
https://packages.debian.org/bookworm/admin/amd64-microcode
Note however that the kernel itself includes mitigations (which can through VyOS config be disabled) and another workaround in the meantime is to update the motherboard BIOS which should also include needed microcode updates (however that method will probably lack 6-12 months if ever updated by the motherboard manufacturer).