I have been at the ONC Interoperability Forum in DC for a few days and I had an opportunity to discuss NIEM for Health with a very well respected former government official whose perspectve I respect very much. He has a long history with standards development, especially in healthcare and with a government perspectivie. The following is his perspective and I tend to agree (I paraphrase here interspersed with some direct statements).
NIEM was established as a government program to create a more consistent way for state, local, federal and tribal governments to exchange information. It has always been funded by federal agencies, and has a governance structure that reflects that. It has been useful in getting law enforcement, government programs, social security, and other programs to exchange information in a consistent way. That is their swimlane. They make standards by government, for government.
OMB Circular A-119 (see https://www.whitehouse.gov/wp-content/uploads/2017/11/Circular-119-1.pdf ) stipulates how government agencies (like ONC) should adopt standards within regulations. It says that the government agencies should adopt consensus based voluntary standards to a preference to Non-consensus, industry, or government-unique standards. NIEM is a "government unique" standard. ONC is required by law to report on all of the standards that ONC adopted through meaningful use, and to explain any deviations from adopting standards that were non-consensus based or government-unique. There are lots of important reasons why governments should not set standards (think of tariffs and other ways to block trade through government specific or company-specific standards that would benefit one group or one company), and so NIEM would need to become a full-fledged real SDO if they are serious about health care.
The NIEM process is not a bad one, but one that is unlikely to scale to encompass healthcare. They are not particularly strong in terminology binding processes, and there is very little knowledge of how the current medical terminologies work.
We should not support government-unique standards that lack shared expertise in healthcare developing yet another set of standards when we desperately need people to mature and use the standards that we already have. Why is it beneficial to organizations to use a new, government unique standard, developed without significant understanding of healthcare, that lacks good mechanisms for vocabulary binding, and that duplicates years of work in HL7, LOINC, SNOMED and other consensus based SDOs?
Unless there is a compelling reason for developing yet-another set of standards in healthcare, change NIEM into a fully transparent SDO, and reinvent the wheel, why would we devote any energy here? Why not use HL7 and FHIR-based standards in prisons so that prisoners get the same level of care and information exchange as people in other parts of the healthcare sector? Why not understand how to interface between human services not only within government (TANF, etc) but also with non-profits, NGOs, and other care agencies? Why would the standards community support yet another standard that has no clear advantages, gets in the way of OMB directives, and pulls resources from other initiatives that would do more good?