Twice annual ICD-10 code updates and more COVID-19 ICD-10-CM/PCS code proposals

September 27, 2021 / By Rhonda Butler

The latest ICD-10 Coordination and Maintenance Committee (C&M) was held virtually Sept. 14-15. First on the agenda, the Centers for Medicare and Medicaid Services (CMS) announced its final joint decision with the Centers for Disease Control and Prevention (CDC) to move to twice annual ICD-10 code updates: April 1 in addition to the October 1 fiscal year update.

CMS/CDC finalized the proposal to broaden the use of the April 1 ICD-10 update beyond its previously restricted use, that allowed only new diagnosis codes for emerging diseases and new procedure codes for qualifying NTAP (New Technology Add-on Payment) proposals. The new, broader inclusion criteria can include both code proposals and addenda items, such as changes to index entries. Changes that have been requested to go into effect April 1 will be labeled as such in the September meeting agenda. 

Proposals labeled for an April 1 implementation date include two ICD-10 proposals for new COVID-19 related codes. One diagnosis proposal and one procedure proposal each were discussed on the first day of the C&M meeting and both involve COVID-19 vaccines.

The National Center for Health Statistics (NCHS) and CDC proposed new ICD-10-CM codes to track underimmunization status. The diagnosis code request is for a new sub-subcategory Z28.31 Underimmunization for COVID-19 status under the existing subcategory Z28.3 Underimmunization status. The proposed new codes are:

Z28.310              Unvaccinated for COVID-19

Z28.311               Partially vaccinated for COVID-19

Z28.39                Other underimmunization status

Audience reaction to this proposal was mixed. Although there was general agreement that the information is of interest and is documented in the medical record, it was not clear to the audience how these new codes would be used, given that the definition of underimmunization for COVID-19 may be a moving target. For example, an immunocompromised person is now eligible for an additional shot of the Pfizer or Moderna COVID-19 vaccine beyond the two shots that currently define “fully vaccinated” according to the manufacturer and the FDA.

Is a person who has not yet received the third shot of vaccine or does not intend receive it, classified as underimmunized? The response given at the meeting—not surprising, really—included phrases like “evolving situation” and “continue to monitor.” Hopefully we will hear more on this subject before April 1 of next year.

If you want to read the full one-page written proposal, it is on page 194 of the diagnosis agenda PDF. The deadline for comments on this topic, and all topics carrying an April 1 implementation date, is Oct. 15. For diagnosis code proposals, send your comments to NCHS/CDC at

Proposed new ICD-10-PCS codes continued the quest for immunization data, with new ICD-10-PCS codes to track hospital inpatient administration of an additional COVID-19 vaccine injection. The interesting thing here is that separate codes were requested for the additional injection, distinguished as:

  • COVID-19 Vaccine Dose 3
  • COVID-19 Vaccine Booster

Audience members said they were confused by this distinction, since the actual injection would contain the same substance (i.e., this is a procedure code and the procedures are identical), and it is not clear what meaning the data would have. CMS responded that “separate codes were requested,” and clarified the intended use of the codes. Dose 3 injection codes are to track the additional injection given to immunocompromised individuals, and booster injection codes are to track the additional injection for booster-eligible individuals.  

CMS further explained that, whereas immunocompromised individuals are considered underimmunized without the third dose, because they need more vaccine to reach an adequate level of immune system response, individuals who qualify for a booster injection are getting that third shot because research indicates that the efficacy of the vaccine wanes with time.

Once explained, it made sense to me as a distinction, and since the reason for the third injection would likely be documented in the hospital record, the coded data could be useful. The audience didn’t sound like they were satisfied. It was apparent that they didn’t much care for the idea of shoehorning the indication for the procedure into the procedure classification. But we have already created separate codes for identical procedures by adding codes for COVID-19 vaccine dose 1 and dose 2.

In the case of the Pfizer/Moderna vaccine, dose 1 and dose 2 are identical procedures. So, here we are. Among the many things that COVID-19 has taught us, sucking it up and adjusting is right up there at the top of the list. We can probably survive this additional deviation from coding orthodoxy if it comes to that.

If you want to read the full proposal, it is on page 49 of the procedure agenda PDF. The deadline for comments on this topic, and all topics carrying an April 1 implementation date, is Oct. 15. For procedure code proposals, send your comments to CMS at

Rhonda Butler is a clinical research manager with 3M Health Information Systems.

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