Delta Strain of COVID — We’re in for a Rough Ride; Napkin Calculation #3

COVID springtime is short. It’s set to end in four more days.

In (CNN) Vaccinated Americans allowed to taste freedom; Not So Fast; Napkin Calculation #2, I wrote:

When B1.351 is vanquished, other variants will compete for dominance, with each other, and with vaccine makers.  Ad infinitum.  Ground Hog Day. Is this certain?  No, but to assume otherwise is wishful thinking.

Fate is now so poised with the Delta variant. The news media are lacking an important comparison, percentage of breakthrough infection. This doesn’t give it:

The above numbers are not comparable. The  casual reader needs elucidation of the meaning. How might we estimate the ratio, protection against infection/ protection against hospitalization?  The Fierce Pharma article does not supply that number.

We can get a rough idea from (Trust for America’s Health, pdf) CDC Data Show High Hospitalization Rates for Diagnosed COVID19 Patients with Underlying  Conditions in the United States, which offers a table, “Diagnosed COVID-19 Patients Age 19 and Older with Known Health History in United States, November [Note: should be February] 12 – March 28, 2020.”

Which row(s) of the table should we compare for an appropriately bracketed estimate?  Both of these:

  • In an early month of 2020, with no vaccine, 9% of those with no preexisting conditions were hospitalized; a ratio of  roughly 10X infected to hospitalized.
  • Including preexisting conditions, 21% were hospitalized; a ratio of  roughly 5X infected to hospitalized.

Currently, 4% of all Pfizer recipients who contract Delta, with or without qualification for preexisting health conditions, are hospitalized. This provides a napkin-calc  estimate of the protection of Pfizer against infection with the Delta strain:

A breakthrough infection percentage of between 5X and 10X the percentage of hospitalized patients, breakthrough of 20%-40%. compared to 5% for the viruses of the original Phase 3 study.

Do we call this “effective against the Delta strain?” Sure, get the shot. The shot improves the outlook for the individual.  It is not good enough to prevent another COVID catastrophe. And there is a strong pure math argument that this level of efficacy will select for an Epsilon strain with even greater breakthrough. It has the near optimal combination of opportunity-for replication, and selectivity.

The failure of the media to correctly portray this comparison verges on managing the news as opposed to reporting it. In defense, “News” might say that “Authorities” have not made the comparison. I say, dig a little, and you’ll get it.

Perhaps the media don’t want to be the killjoys. Somebody has to do it, and it’s their job. We will soon don masks again, retreating to our private amusements. Perhaps after the vaccines are adjusted with boosters, we can ditch the masks — for a while.

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