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CDC UCoD swapping

A Primer on Our Methods, and the Significance of UCoD Swapping


I imagine that almost anyone reading this is by now familiar with the propensity for coroners, doctors, and other medical professionals up and down the medical community to document covid as a clinical condition in patients where it was medically unjustified. This led to a massive number of ‘fake’ covid cases or deaths.

We are trying to highlight here an entirely distinct phenomenon that occurred within a subset of deaths where covid was documented as a Cause of Death (CoD), which we are calling ‘UCoD swapping.’

The significance of the UCoD

It is critical to understand the following specific definitions to follow this article:

This is what it looks like on an actual death certificate (read the instructions):


The UCoD designation is to highlight the condition or injury that was the primary catalyst or cause of the death or the chain of events precipitating the death.

The CDC’s role in assigning the diagnostic codes from the ICD-10 database

There is one other factor necessary to understand ‘UCoD swapping.’

In epidemiological databases such as the CDC’s Wonder datasets, medical conditions are recorded using diagnostic codes, not the text description of the medical care provider documenting the condition.

For death certificates, diagnostic codes from the ICD-10 database are applied by the CDC to all of the conditions stipulated on a death certificate as a CoD. (Well, maybe not always.)

Critically, the CDC designates one of the ICD codes it applied to the death certificate as the UCoD. In theory, the ICD code designated by the CDC as the UCoD should match the condition listed as the UCoD on the death certificate. However, in reality, there are numerous instances where the CDC assigns the UCoD designation to a condition other than the one stipulated by the death certificate as the UCoD.

Is this fraud per se? Not necessarily. Most medical professionals have no idea how to properly fill out a death certificate, something documented by numerous studies showing a high rate of significant inaccuracies or errors in death certificates, including the CoD’s.

UCoD swapping to designate covid as the UCoD on death certificates where covid wasn’t documented as the UCoD

The principal significance of UCoD for us is that it provides an additional method or pathway for increasing the number of “covid deaths.” By falsely designating covid as the UCoD on death certificates where a different condition is listed as the UCoD, the CDC could make covid look far more lethal. This could also conceal a substantial portion of deaths in mortality datasets that might otherwise be more readily identified as cases of “died with covid” where covid was unlikely to have been a clinically significant factor in the death.


I previously published a list of the conditions that were documented as the UCoD on a death certificate where the CDC nevertheless designated covid (ICD code U07.1) as the UCoD when it applied the ICD codes — the ‘UCoD swap.’

I along with John Beaudoin (Coquin de Chien on Substack) and a few others have possession of the death certificates covering all deaths from the states of Massachusetts and Minnesota going back to 2015. 

Since these death certificates have the ICD codes applied by the CDC, we can compare the ICD codes to the text descriptions of the CoD’s on the death certificates. This enabled us to search for death certificates where the UCoD condition assigned by the CDC didn’t match the UCoD condition listed on the death certificate, specifically where the mismatched UCoD assigned by the CDC was U07.1 (covid).

Our search methodology was as follows:

  1. I added a column to the spreadsheets containing the death certificates for ‘UCoD Text.’ This was done by an Excel formula consisting of 4 nested ‘if’ conditions starting from Cause D using the following parameters: If Cause D =/= blank, UCoD = Cause D; else, if Cause C =/= blank, UCoD = Cause C; else, if Cause B =/= blank, UCoD = Cause B; else, UCoD = Cause A.
  2. I isolated all deaths with a UCoD of U07.1 using Excel (the spreadsheets already contained a field identifying which ICD code was designated by the CDC as the UCoD).
  3. I eliminated all deaths that contained any sort of reference to covid in the text description of the UCoD condition. This was accomplished by sorting the UCoD text fields in alphabetical order and manually removing all deaths where the UCoD text referenced or described covid. Anything that could be in any way construed as somehow describing covid as a CoD was eliminated.
  4. Using Excel, I eliminated duplicates of identical text descriptions of non-covid conditions to create the final lists of non-covid UCoD conditions that were published on Brownstone. The number of these UCoD deaths for each unique text description was calculated using the Excel Countif function applied to the set of death certificates containing a UCoD of U07.1

Important Caveat

This list is not meant as a final product showing all deaths where the CDC fraudulently applied a UCoD of U07.1. Applying a UCoD other than the one stipulated by the death certificate could be justified where the death certificate was clearly filled out erroneously and it is obvious based on the totality of information presented in the death certificate which of the other conditions identified as a CoD should have been identified as the UCoD would the coroner have filled out the death certificate properly.

Published under a Creative Commons Attribution 4.0 International License
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  • Aaron Hertzberg

    Aaron Hertzberg is a writer on all aspects of the pandemic response. You can find more of his writing at his Substack: Resisting the Intellectual Illiteratti.

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