Chicago's Dastardly Definitions and Disappearing Data During the "Delta" Wave

A Windy City example of the kinds of "vaxed/unvaxed" data shenanigans that were used in many places around the world

This is a throwback/“for-the-record” post from the days when I was focused on Chicago’s so-called “breakthrough” reports. (

Norman Fenton

Martin Neil

Clare Craig

and

Mr Law, Health and Technology

’s good work on ONS data shenanigans brought it to mind.)

Here I reproduce a September 2021-March 2022 Twitter inquiry, with slight edits for clarity and style.

I will not forget how Chicago officials’ used data distortion to shame “the unvaccinated,” coerce unnecessary shots, ban people from public places, and threaten city workers’ jobs.

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September 24, 2021 [original thread]

I obtained the data underlying the Chicago Department of Public Health’s September 4th breakthrough report via FOIA. It’s hard to interpret due to CDPH’s definition of vaccinated, but let’s give it a shot. #punintended

Since July, 35% of cases are among vaccinated residents (n=7,410/20,623).

What does vaccinated mean? Per CDPH, "completion of vaccine series at least 14 days prior to a positive test, with no other positive tests in the previous 45 days.”

So unvaccinated includes people who tested positives and have received

• Zero doses

• 1 of 2 doses

• 1 of 1 dose or 2 of 2 doses, less than 14 ago

• 1 of 1 dose or 2 of 2 doses more less than 14 ago but who tested positive within the past 45 days

This is a hot mess for the data. (See Gato’s article for related issues.)

Around 20% of Covid hospitalizations since July have been vaccinated folks (n=295/1140).

This data doesn't capture vaccinated or unvaccinated long-term care facility residents who aren't sent to the hospital. We also don't know if this is people hospitalized with Covid or because of Covid.

With Covid-related deaths, the raw weekly number remains on the low side. Since July, 13% of deaths attributed to COVID have been vaxed ppl (n=20/156). The problem of saying any death within 30 days of a Covid test as a Covid death still exists.

Compared to this time last year, Chicago's Covid hospitalizations are higher, but deaths are lower (for now). The oldest groups still have the highest rates of hospitalizations & deaths, but the average age of a COVID-related death occurring between June 27 and September 4 is 65.

The total number of unvaccinated and vaccinated Chicago residents from week to week is a bit wonky.

I understand that age-based eligibility changed over the course of spring 2021, but I don't understand the back and forth with the total and welcome any explanations.

Note: The reason I started my graphs in with July is because cases were already on the decline in April, when vaccination opened to everyone age 16+. The Mayor [Lori Lightfoot] and @DrArwady are fond of quoting stats from January 2021 onward, but that is mixing too many apples and oranges, in my opinion.

To be clear, I am NOT trying to sow doubt in the efficacy of vaccines. I take issue with mandates, not with people making the choices that are best for them.

But claims that Chicago is experiencing a "pandemic of the unvaccinated" are unsubstantiated by available data. “Vaccinated/unvaccinated” is a misleading dichotomy. More transparency is needed.

In a few weeks, I'll request updated data, and we'll see what it shows.

October 1, 2021 [original thread]

The Case of the Disappearing Data

I’m concerned about data that seems to have disappeared from the Chicago Department of Public Health’s vaccine breakthrough reports.

I don’t want to accuse anyone of fraud or misrepresentation yet, which is why I invite other eyes to see if they see what I see.

Here’s CDPH’s first “breakthrough” report, issued on August 18, 2021.

Rates for three groups are shown: Unvaccinated, Vaccinated (1st dose), & Fully Vaccinated.

Definitions for two of the groups are provided in the footnotes.

Vaccinated is defined as “having at least one dose prior to a positive test. Fully vaccinated is defined as “completion of vaccine series at least 14 days prior to a positive test.”

So Chicago residents who received doses less than 14 days ago are not broken out as a separate group and a full dose would include residents who received the one-dose Johnson & Johnson shot.

The footnotes also say the data includes specimen collection from as far back as 1/1/2021. It's unclear whether the first reporting week shown (March 6) represents data from Jan 1, 2021 - March 6, 2021. (Given Chicago's weekly case numbers in those months, I assume not.)

Now look at the Aug 21, 2021 report.

There’s no change to unvaccinated (red line) or fully vaccinated (solid blue line). The vaccinated (1-dose) group is gone and the vaccinated definition is mistakenly still in the footnotes.

Where did the “1-dose” folks go?

Here are the Aug 18 and Aug 21 rate graphs alongside one another, so you can see the disappearance more clearly.

Also note the vaccinated & fully vaccinated lines in the Aug 18 report converge in May/June. (I'm not sure why but I am glad to hear people’s insights about why.)

One week later, in the 8/28 report, the footnotes have been cleaned up and the definition of fully vaccinated revised to include “with no other positive tests in the past 45 days” That change doesn’t appear to have changed the fully vaccinated rates, but it does raise questions about what the the revision excluded henceforth.

I submitted a FOIA today to CDPH for the underlying data in the Aug 18th report. I have the raw data for the Sept 4th report - about which I tweeted earlier this week.

Before I reviewed the Aug 18th report, I posted a question to CDPH Director Alison Arwady asking her why the city’s breakthrough data doesn’t delineate more-accurate groups. She responded. Take a listen:

Arwady said:

• The city has the data.

• They've published some of it in the past.

• Fully vaccinated is full protection “from COVID”.

• 1 dose of the Johnson & Johnson vaccine is fully vaccinated.¹

To that, I say:

• Why isn't the city publishing the data now and why did it remove 1-dose data after Aug 18?

• Why the Aug 28 change to the "fully vaccinated" definition? Whom did that exclude?

• Yes to J&J = fully vaccinated, but where’s the 1 of 2 dose data? And the full dose/<14 days data?

Covid-related deaths in Chicago & Cook County are up compared August/September 2020.

I am NOT saying the vaccine is or isn't playing a role.

I AM saying vaccination data must be transparent, crystal-clear, and void inaccurate dichotomies. I will post more about this when I receive a response to my FOIA request.

December 3, 2021 [original post]

UPDATE: I did get a response to this FOIA, but it did not include the 1-dose data. 🤦‍♀️

March 15, 2022 [original post]

Chicago DPH "clarifies" definitions in its vaxed/unvaxed data at last. So, "unvaccinated" = "unverified" vax status - and partial dose folks are omitted from the dataset. Yikes.

Release the partial-dose data @DrArwady.² We both know you have it.

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Next post

"It is Challenging to Determine the Relationship Between a SARS-CoV-2 Infection and the Reason Someone was Hospitalized or Passed Away"

1. I didn’t include it in the summary at the time, but Arwady also said, “With Delta, it’s actually not enough to be partially vaccinated.” Like many public officials across the U.S. in those days, Arwady’s messaging on the Delta variant was insistent on it being more contagious and possibly more resistant to the vaccine. One of my theories about Delta is that it was (in part) a scheme to hide the vaccine inefficacy via the maltreatment of “the unvaccinated.” The Governor of Illinois’ message in those days was “Delta is different”.

2. Alison Arwady is now Director of the National Center for Injury Prevention and Control at the CDC.