If networking is required, then private networking is the next best protection. Even so, it is likely that public network infrastructure will be used somewhere in the inter-network. Hardware-based encryption provides the best protective barrier for information flowing over public networks. It is unlikely that voice communication would be considered vulnerable in a network carrying health information. Far more vulnerable are facsimile and data communications.
Facsimile machines are ubiquitous and cheap.
It would be difficult to find a business without one. Many individuals also possess a fax machine. New Internet services are evolving that provide facsimile and e-mail gateway services. It is not difficult, technologically, to develop other sorts of facsimile gateways. It is rare that someone would consider protection of facsimile communications.