Fact Check-Claims of ICD-10 codes used to track unvaccinated individuals missing context

New diagnostic codes that describe a patient as under-immunized against COVID-19 were introduced to help doctors identify patients potentially at risk for more-severe COVID and to help health officials track vaccine effectiveness and mortality statistics, among other public health questions, not for U.S. government tracking of unvaccinated individuals, as some are claiming online.

The codes in an individual’s medical record, like all personal health information, are protected by U.S. privacy law and could only be analyzed at the group or population level uncoupled from individual identities, medical experts told Reuters.

Yet users are sharing news of the 2022 update as evidence that governmental agencies will now be tracking unvaccinated individuals who go to the hospital or see a doctor as part of a “surveillance program,” with comments implying that users think they will be personally identified.

Examples can be seen (here) (here) and (here).

The remarks refer to a 2022 update to the ICD-10 (the 10th revision of the International Classification of Diseases), which added code Z28.31 “Underimmunization for COVID-19 status” – including sub-codes representing unvaccinated or partially vaccinated – to an existing general code Z28.3 representing “underimmunized,” which can be viewed on page 194 of a Centers for Disease Control and Prevention (CDC) document (here).

The larger Z28 category is longstanding and used for reporting when any type of immunization is not carried out during a medical encounter for a variety of reasons (here ). All medical providers covered by the Health Insurance Portability and Accountability Act (HIPAA) have used the codes since at least 2015, according to the CDC (here), ( ).

Eric Burnett, who specializes in hospital and internal medicine at Columbia University, (here), told Reuters that ICD-10 is a “common language” and allows healthcare professionals “to collect data on specific conditions to improve patient care and clinical outcomes.”

These codes are not used with purposes beyond monitoring and reporting diseases and mortality statistics or for insurance billing, and non-healthcare personnel would not have access to codes with specific patient identifiers, as that would be a (HIPAA) violation, he said.

Bert Kelly, a CDC spokesperson, told Reuters that the agency can analyze ICD 10 code data on vaccination status, but the CDC and the National Center for Health Statistics (NCHS) “are not tracking individuals,” as the data is “analyzed without any personal identifiers.”

Some non-HIPAA covered agencies do have access to the ICD-10 codes, Burnett added, “but they are not associated with specific patient identifiers,” meaning they “won’t know what patient has which ICD-10 code.”


The Z28 codes that report general underimmunization status are not new, Burnett said, but its subcategories were updated to reflect COVID-19 vaccination status “simply because COVID-19 vaccines are new vaccines.”

A proposal to create a COVID-specific underimmunization status subcategory with three new codes was first introduced at a CDC ICD-10 meeting in September 2021 (see page 194) (here).

The 2021 proposal specified that underimmunization for COVID is a “significant modifiable risk factor” for severe disease and death and “of interest for clinical reasons as well as for public health.”

Some social media posts highlight the proposal text stating “there is interest in being able to track people who are not immunized or only partially immunized,” but Burnett said the word “track” in the proposal “does not mean the government is going to keep tabs on unvaccinated individuals for punitive reasons.”


Burnett said healthcare professionals may want to know a patient’s vaccination status to address vaccine hesitancy, assess risk of severe infection and analyze vaccine efficacy, none of which “are sinister in nature.”

“It lets us know their risk for contracting a specific vaccine-preventable disease, it reminds us to counsel them on the benefits of vaccination,” he said, which can help professionals “provide evidence-based education specific to a patient’s concerns on immunization.”

He said the ICD-10 codes could also help track data on vaccine efficacy, including comparisons between vaccination statuses of hospital or ICU patients with COVID, or patient mortality data based on vaccination status.

Reuters Fact Check debunked a similar claim about ICD-10 code Z28.20 used to place unvaccinated individuals in education camps (here).


Missing context. ICD-10 codes are not new, and the COVID-underimmunized codes added in 2022 are not used to track individuals for reasons other than monitoring vaccination status to assess vaccine efficacy and analyze mortality data.

This article was produced by the Reuters Fact Check team. Read more about our work to fact-check social media posts (here).