Virtual network service endpoints are generally available for Azure Key Vault in all public Azure regions.
Azure customers use Azure Key Vault to safeguard application secrets, certificates, and encryption keys for their cloud applications. Virtual network service endpoints provide an additional layer of security to key vaults by adding firewalls and virtual network rules. With this feature, you can lock down access to your key vaults so that the key vault data plane is accessible only from designated virtual networks or IPv4 address ranges.
For up-to-date details, refer to the documentation.