As of September 20, more encouraging signs have emerged suggesting that the current delta variant wave of COVID has peaked in most of the US.

Hospitalizations

US hospitalizations declined over the last three weeks, dropping from ~93,000 to ~80,000 or about a 14% decline.  The decline appeared to be accelerating in the last few days.  The new hospitalizations data was even more encouraging as it dropped by nearly 21% (12,362→9,769).  If the late August highs hold, the delta wave will have peaked at about two-thirds of the January high.

There is some regional differentiation.  The Mid-Atlantic and MidWest are continuing to see rising hospitalizations; however, those are being offset by dramatic declines in the South.  This is the chart for new hospitalizations in Louisiana.

Frankly, the chart almost looks too good to be true.  There may be some holiday and storm disruption reporting issues contributing to this decline.  But similarly, if somewhat muted, declines are happening across all of the states that were the hardest hit by delta.

Hospitalizations in Texas have finally begun to decline.  From the low of 1,428 on June 15, hospitalizations skyrocketed to a peak of 13,952 on August 25.  That was nearly a tenfold increase in less than two months.  Since then, hospitalizations have been steadily trending down, reaching 11,710 on September 19 (-16%).  ICU bed usage also rose sharply in July and August, although not quite as dramatically, but has also been slower to recede.

The CDC’s new admissions data for Texas has made a distinct downturn. (Note that the data in the gray bar to the far right side of this chart is preliminary and likely not complete.)

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The decreases were fairly uniform across the State.  The only two regions that had notable increases were DFW and Wichita Falls.

Fatalities

As I warned in my last report, the CDC has made some significant backdated adjustments to fatalities.  Texas apparently made a significant contribution to the backdated fatalities.  The CDC is now showing the seven-day average at the end of August to just over 1,400, compared to its earlier estimate of just over 1,000.  Currently, the CDC shows the fatalities during September moving with a range of 1,350-1,520.  Of course, fatalities are always the ultimate lagging indicator and I suspect they have even more noise with delays around the holiday and the storms in the South.  I think we will need to see how this number settles out over the next couple of weeks before inferring too much from the current data.

With a significant number of backdated deaths, the Texas date of death analysis now shows that fatalities probably peaked at the end of August at about 270.  That analysis shows a distinct decline since the end of the month but, again, I would not trust this trend until we get past any potential holiday/storm-related reporting disruptions.

The rise in fatalities has begun to push up the numbers on the CDC Excess Death Analysis.  It is now showing that excess deaths in mid-August were running at about 20% above what would be normal for that time of year.  This will probably drift a bit higher as more reports trickle in.  So far, the excess deaths from the delta wave are significantly below the January peak when excess deaths were running more than 40% above normal.    

Vaccines

The rate of vaccinations, which had been rising since July, have now begun to slide again.  The seven-day average at the end of August topped out at about 830,000 per day.  Since then, the average is down to about 650,000.

As a result, the percentage of the US population fully vaccinated continued to increase, albeit at a slower pace, moving from 52.6% at the end of August to 54.7% yesterday.  The rate for seniors increased by just over one percent (81.8%→82.9%).  Similarly, the number of seniors with one shot rose from 92.1%→93.2%.  I thought we would hit a ceiling at some point but so far more seniors continue to make the decision to be vaccinated.

The rate of new vaccinations in Texas continued to outpace the national average and it finally broke the 50% mark (47.6%→50.3%).  Texas continues to lag behind the national average but is gradually closing the gap.  Texas currently ranks 28^th of the 50 states in the percentage of the population fully vaccinated.  

The over-65 fully vaccinated number in Texas increased a little over one percent in the last three weeks (78.0%→79.1%).

Testing Results

Nationwide, testing has continued to rise to about 1.6 million tests per day.  The CDC increased its daily seven-day average of “new cases” to 160,000 as of the end of August.  Since then, it is showing a slow, uneven decline, falling to about 140,000.  It shows even a more dramatic decline in the last few days but I am skeptical about that data.  This is well below the peak of about 250,000 per day in January.  Also, recent research is suggesting that we may be catching about half of the infections with testing today, compared to probably less than a third in January.  The current nationwide positivity rate is 8.6%

Texas’ seven-day average for “new cases” has bounced around over the last three weeks in the range of 13,000-15,000.  The data in the last few days in showing a fairly dramatic move downward but, again, I would not infer too much from that preliminary data just yet.  The positivity rate for the State’s date of specimen testing has persistently hung in at about 15%.  I don’t put a lot of stock in the positivity rate but I do find that metric not moving a bit concerning.

Conclusion

I think the best way to think about the ebbs and flows of COVID is to compare them to a playground seesaw.  It takes very little change in the weight on either end to move it from all the way up to all the way down. In this case the weight on one end is immunity (natural and vaccine-induced) and on the other end is the virus’ ability to evolve to become more contagious.  The degree of our suppression efforts (“NPIs”)can also add to or subtract weight from one end or the other, although I doubt NPIs are as nearly consequential as the underlying biology.

At wave peaks, as we have apparently seen over the last few weeks, the weights balance momentarily before moving the seesaw the other direction.  But once the tipping point is reached – either direction – the opposite move tends to be dramatic and rarely reverses once the move starts, at least, until the next trough or peak is reached.

There has been a lot of discussion in the media about “breakthrough” cases, i.e., people getting COVID after they have been vaccinated or recovered from a previous infection.  Despite all the hype, breakthroughs are not common and are in line with what we should have expected based on the data we had on the vaccines’ efficacy.  While breakthroughs have contributed marginally to the current delta wave, the vast majority of the cases, and especially the cases of serious disease, are occurring in the unvaccinated population.  I plan to write about the breakthrough statistics in more detail in the next week or so.