The CDC's latest mask guidance, much better, but still not good enough

Last update: Sunday 3/6/22 

This blog note is the third part of a two-part series, meaning:  the blog's editor planned two parts, but a few days after he posted the second part his growing misgivings about the CDC's February 2022 guidance compelled him to add this "final" note to the series. The CDC's guidance to U.S. counties was based on their local hospital resources. As such, it was a giant step beyond the CDC's usual "one size fits all" recommendations. Unfortunately the guidance didn't go far enough. This note addresses two shortfalls.

1. Insufficient warning to the most vulnerable residents of a county

The bullets in slide #7 of the CDC's PowerPoint PDF identify the two metrics that underly the new levels proclaimed by the CDC on 2/25/22:

• "New hospital admissions with confirmed COVID-19/100,000 people and ... "
  
• "Percent of inpatient beds occupied with COVID-19 patient"

Combinations of these metrics were used to specify three "COVID-19 Community Levels" ==> low, medium, and high, as specified in slide #12. A copy of this slide appears below:

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According to the "How CDC Measures the COVID-19 Community Levels" section of the "" page:

• "The COVID-19 Community Level is based on the higher of the new admissions and inpatient beds metrics."

While these metrics are plausible indicators of strain on the capacity of local hospitals, the "medium" and "high" would not be computed until a surge in hospitalizations had actually begun; hence they would not provide timely warnings of impending hospital strain. 

Under previous variants, surges in hospitalizations usually followed surges in new cases of infection by a few weeks. Unfortunately, as many as half of the new cases from Omicron are breakthrough cases, i.e., fully vaccinated persons. Only a small percentage of breakthroughs become severely ill, so surges in new cases are no longer reliable predictors of comparable surges in hospitalizations.

Therefore the CDC framed its metric in a breakpoint for new cases shown in the first column of the table. The first two rows are applicable when there are fewer than 200 new cases per 100,000 county residents every 7 days; the last two rows apply when there are 200 or more cases. Ideally, this breakpoint would occur after the new cases began to surge, but before the hospitalizations began to surge. 

In summary, the number of new cases are ignored until they reach 200 per 100,000 county residents. That's fine for hospital administrators because want to receive warnings about impending surges in severely ill cases. However it is not fine for the most vulnerable residents of a county, i.e., its immunocompromised and oldest residents because they can be infected by brief contacts in public indoor spaces with breakthroughs who only have mild or even asymptomatic Omicron infections.

The CDC took a gigantic step away from its usual "one size fits all" guidance by placing a county guidance app on its Website, a copy of which appears below. Readers can obtain Covid levels (high, medium, or low) for each U.S. county from the app by selecting a state and a county from the drop-down lists in the input box. The app returns the COVID level of the county together with the CDC's mask guidance for that level.  That's how this version of the CDC's guidance acknowledges that different counties might need different guidance. 

The app falls short in not recognizing that different persons in the same county might need different guidance. The app should require its users to mark checkboxes to indicate whether they are fullly vaccinated, are boosted, are immunocompromised, and are at least 65 years old. The breakpoint for persons who select these boxes should be much lower than 200, say 100 or even 50 new cases in 7 days. Low level "green", no mask guidance might be returned by the app to less vulnerable residents of a county; whereas more vulnerable residents might receive high "peach" guidance because the public indoor spaces in the county embody more risk to its more vulnerable residents. They should receive stronger guidance, e.g., recommendations to wear N95 masks,  maintain social distancing, avoid large groups, etc, etc, etc. Otherwise, nearby asymptomatic maskless breakthroughs in public spaces may pose mortal danger to a county's most vulnerable residents.

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2. Proof by "pretty maps"

The "COVID-19 Community Levels" presented in the CDC's February 2022 guidance replaced the "Indicators of Community Transmission" that the CDC had presented in September 2021 because the CDC asserts that the new levels provide a more reliable measures of the threat posed by the virus. 

One would therefore have expected tables and/or maps that showed how the low, medium, and high categories of the new levels matched th hospitalization data in all U.S. counties better than the low, moderate, substantial, and high categories of the old indicators. But alas, the CDC's February presentation only provided thematic maps of all U.S. counties colored by the assigned levels and maps of U.S. counties colored by the assigned indicators; no data for hospitalizations was mapped. Of course these data-free displays did not prove which was more reliable, but, ironically, they undermined the viewer's confidence in the new levels. 

Before looking at the side-by-side maps in the copies of the CDC's PowerPoint slides that appear below, let's review some relevant fundamentals that most of us have come to believe:

• Our vaccines and boosters are highly effective in preventing severe illness, i.e., in preventing illness that can only be treated in hospitals
• Most blue states have higher vaccination rates than most red states.
• Blue states have lower hospitalizations rates than red states
• Delta was our most lethal variant so far, i.e., Delta caused more severe illness per 1,000 people it infected than other variants

Now let's look at the pair of maps based on hospitalization data on November 5, 2021. The CDC's PowerPoint presentation declares that November 5, 2021 was "between Delta and Omicron", but that's not true, as per the following NY Times report, in which Dr. Fauci says that the first case of Omicron in the U.S. was detected on December 1, 2021. 

• "U.S. Reports Its 1st Omicron Case, in a California Traveler", Michael D. Shear, Shawn Hubler and Roni Caryn Rabin, NY Times, 12/1/21 

But that misstatement by the CDC is not the problem. The problem is what the maps declare, no matter which variant was involved.

• Look at all of that pretty green in the map on the left side of the slide, the green level whose guidance from the CDC's app is "no masks"
• Now look at where you see the most green ==> in the Southern reddest of GOP states, the states whose governors opposed all mandates, including vaccines and masks. 

Not quite what you expected? Were the GOP governors right??? ... Or is the CDC's guidance app not quite as reliable as it should be?

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Links to related notes on this blog:  

• "The CDC's new guidance for masks concedes that one size does not fit all", Last update: 3/1/22
  
  
• "Rationale for the CDC's new guidance for masks", Last update: 3/13/22