Finally, the CDC has released some interesting data…

In case you missed it, last week the CDC released a study (with data!) on vaccine efficacy.

Specifically, the CDC researchers looked at emergency room and urgent care visits and hospitalizations in large participating medical centers in  10 states.

The data was gathered from August 2021 thru January 2022, when both delta and omicron variants were in circulation.


WaPo’s headline:


“mRNA booster shots  lose effectiveness after about four months — but still provided significant protection in keeping people out of the hospital during the omicron surge.”

In numbers, the boosters provide 91% protection from hospitalization right after vaccination … and 78% protection 4 months out.


My opinion: That’s formidable protection … and, not really new news.


Drilling Down

What I found more interesting (with some new news) was buried in the report’s exhibits.

Teaching Point: I used to tell students to always start cases by going through the exhibits before even starting to read the case narrative.

Here’s my recap … below are my takeaways…


> Again. the data was collected from large participating medical centers (and their urgent care affiliates) in  10 states. A representative sample, reporting high quality (consistently defined) data.

> Over the 6-month study period, 241,204 patients (row 3, column 1) visited an Emergency Room (ER) or Urgent Care Center (UC).

> Of the 241,204 … 54% had been vaccinated, 46% hadn’t. That’s roughly the country’s mix with minimal skew one way or another.

Point of interest: That mix doesn’t sync with the widespread narrative that ERs and UCs being entirely overrun with unvaccinated people.


> Of the 241,204 ER/UC visits … 61,826 (25.6%) tested positive for covid.

The 1 in 4 number strikes me as being low low  since, I presume, the vast majority came to the ER/UC with covid-like symptoms 

> Drilling deeper, 14.4% of the vaccinated patients tested positive; 38.8% of the unvaccinated patients tested positive.

So, in a relatively balanced sample, unvaccinated patients accounted for about 70% of the positive covid results.


> Of the 241,204 ER/EC patients, 93,408 (38.7%) were hospitalized;

> Of the 110,873 unvaccinated patients, 32.6% were hospitalized; of the 130,131 vaccinated patients 40.9% were hospitalized.

In other words, a higher percentage of vaccinated patients ended up being hospitalized.

Now, that’s interesting, isn’t it?


Drilling down on Demographics

> Patients visiting ERs & UCs were split 72.5% under 65 and 27.5% 65 and older.

> 73.9% of the 65+ were vaccinated; only 46.5% of the <65 were vaccinated

> Commensurately, only 19.3% of the 65+ tested positive for covid; 28% of the <65 tested positive

> But, 75% of the 65+ were hospitalized; only 24.9% of the <65 were hospitalized

> Of those who were hospitalized, only 23% had tested positive for covid.

Said differently, over 2/3s of the hospitalized patients were admitted to the hospital for something other than covid.

That, in my opinion, is the most interesting number!

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