Category: COVID through 2022

All my various postings tracking the COVID-19 pandemic through the end of 2022.

Post #1450: COVID-19 trend, a continued 30%/week decline, no “endemic rate” in sight.

 

The U.S. is now at 16 new COVID-19 cases per 100K population per day, down 30% in the past seven days.

We now have eight states with single-digit daily new case rates.  That’s nice.  But what’s nicer is that rates continue to fall at a rapid clip, even in those low-rate states.  This suggests that whatever our “endemic” level of Omicron is, it’s likely to be low.

As with just about everything else about this pandemic, I don’t think anyone would have predicted that.  Certainly not based on the extremely contagious nature of Omicron.

And, to be clear, we’re not seeing the same thing in Europe or Australia.  At least, not yet.  So this doesn’t appear to be any intrinsic property of Omicron, but somehow depends on the circumstances.

Continue reading Post #1450: COVID-19 trend, a continued 30%/week decline, no “endemic rate” in sight.

Post #1449: A quick note on cost-effectiveness of Paxlovid-for-all.

 

The Federal government has announced a policy of providing Pfizer’s anti-viral drug Paxlovid for free, to anyone with a positive COVID-19 test.  I believe that a key aspect of this plan is that you can bypass going to a physician for a prescription.  Hence, in theory, it will be immediately available to anyone with evidence of a positive COVID-19 test.

This drug is an anti-viral, that is, it interferes with viral DNA/RNA replication.  (This news reporting explains that point, along with the proposed policy.)  The idea behind providing this drug is to prevent severe COVID-19.  With luck, the anti-viral will slow down the COVID-19 enough that a person’s immune system can tackle it without the need for hospitalization.

Paxlovid is advertised as having reduced the risk of hospitalization from COVID-19 by 90%.  But that’s not true.

Or, to be more precise, it’s not true for the average person who tested positive for COVID-19.  If you actually read a summary of the clinical trial, Paxlovid resulted in a roughly 90% reduction in hospitalization for:

  • Persons with a positive COVID-19 test
  • whose symptoms began less than five days earlier,
  • and who had not yet been hospitalized,
  • who had at least one significant comorbidity,
  • And were unvaccinated
  • And had no prior COVID-19 infection
  • And who were not expected to receive monoclonal antibodies.

You can read a summary of the details at this reference.  But all you really need to read is the title, which is:

Source:  Same reference as above.

In other words, this drug reduced hospitalizations by 90% when it was a) the only treatment offered to prevent hospitalization, b) in a population with a high likelihood of hospitalization.

In particular, note that this drug was only given to individuals with no prior immunity to COVID-19.  That means no vaccine, and no history of infection.  By themselves, those two factors would likely have eliminated 90 percent or more of the U.S. adult population as being candidates for use of this drug.

I’m just trying to point out the vast gap between the population that the drug was tested on (those at high risk for hospitalization) and the population that can now receive the drug for  free (any adult with a positive COVID-19 test). 

Recall that vaccine/booster already reduces risk of hospitalization by about 90 percent (immediately following the booster shot).  And that hospitalizations are highly concentrated among the elderly, and those with multiple risk factors.

Given that, it’s a pretty fair guess that if you give this drug to everyone — vaccinated or not, elderly or not, high-risk or not — you aren’t going to achieve anything like a (further) 90% reduction in hospitalizations.  Most of the people you’d be giving this to would be at only the slightest risk of hospitalization in any case.

A  crude cost-benefit calculation

The Feds will be shelling out $530 per course of treatment with Paxlovid. Not that anybody ever worries about cost.

The last time I looked into it, the average COVID-19 hospitalization cost somewhere between $20K and $25K.  That was based on a then-current analysis of the cases covered and paid by Medicare.

Just looking at the round numbers, in order for Paxlovid to be cost-effective, for every 100 courses of treatment provided (at a cost of about $50,000), it would have to eliminate two hospitalizations (at a cost of about $25,000 each).

Sure, that’s only focused on the hospital facility bill.  There may be disability beyond that, there will certainly be physician and other bills beyond the facility bill.  There’s always the issue of the value of life (the dollar value assigned to preventing avoidable deaths).

But in a crude sense, to be roughly cost-effective, this drug needs to avoid two hospitalizations for every 100 courses of treatment given.

That raises an obvious minimum question:  For what segment of the population does the crude case hospitalization rate for Omicron exceed 2 percent?  That is, assuming this drug would eliminate all hospitalizations, for what portion of the population would this likely be cost-effective?

I have to do this by approximation, because there’s no single data source that lets me get at the answer.  But as I weed-whack my way though the available data, among readily-identifiable groups, I get the sense that only the unvaccinated age 40+ have an Omicron case hospitalization rate in excess of 2 percent.  (To those individuals you could plausibly all individuals age 85+).

Best guess, doing a quick back-of-the-envelope, about 15 percent of the U.S. adult population falls into the category of age 40+ and unvaccinated.  Even assuming this drug absolutely eliminates the possibility of hospitalization, it’s not cost-effective for perhaps 85% of the population that’s now going to be eligible for it.

Contrast to vaccines.

Here’s what I find so odd about this.  It’s not just about the money.

It’s not as if this drug is plentiful.  To the contrary, near as I can figure, the U.S. will only buy enough pills for roughly 100,000 courses of treatment in March, upping that to 200,000 courses of treatment in April.  (That’s based on stated counts of pills, from this source, with a five-day course of treatment requiring ten pills).

Contrast the 100,000 courses of treatment per month to the 58,000 new cases per day that we’re seeing currently in the U.S.  The U.S. is buying enough doses to treat a few percent of new cases.  But they’re making those doses available to 100 percent of new cases.

The last time a COVID-19 treatment was scarce, and made freely available, the government restricted access to those most in need.  And here, I’m talking about vaccines.  Vaccines were first made available to the oldest old, then to higher-risk persons within the general population.  And only after those high-risk populations were taken care of could the average low-risk individual receive a vaccine.

By contrast, here we have a drug that was only tested for the highest-risk population:  Individuals with comorbidities indicating high risk, and with no prior immunity (from vaccine or from prior infection).  But for this latest treatment, the stated policy is a straight-up first come, first served. 

I can’t quite grasp what’s changed.   Maybe the Feds think that nobody’s going to want this treatment.  Maybe they figure that most cases are mild enough that people won’t demand a this free anti-viral.  (But that never stopped people from demanding useless antibiotics to treat colds and flu.)  Maybe this is just a confidence-building measure.  No matter who you are, you can be assured that if you get COVID, you’ll have immediate access to this treatment?  So the impact is intended to be more psychological than medical?

Beats me.  All I can say for sure is that’s an oddity to test a drug on one highly-circumscribed population, and then make that drug available to all comers.  I don’t believe I’ve ever seen that before.

This still has to get Congressional funding to be implemented.  At $500 a throw, you’d think somebody in the Congress would use the lack of cost-effectiveness as a reason to impede the President’s initiative, regardless of its merits or lack of merits.

I guess we’ll see how this plays out.  But I just can’t see this sailing through the Congress with nobody questioning the discrepancy between the target population for this drug, as tested, and the target population for this drug, as delivered.

Post #1447: COVID-19 trend to 3/1/2022, better here than elsewhere.

 

New U.S. COVID-19 cases continue to decline, but at a slower rate.  As of today, the U.S. stands at 18 new COVID-19 cases per 100K population per day, down 28% in the past week.  That contrasts to a 42% weekly rate of decline just one week ago.

Data source for this and other graphs of new case counts:  Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 3/1/2022, from https://github.com/nytimes/covid-19-data.”  The NY Times U.S. tracking page may be found at https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html

Even with that slowdown, the U.S. seems to be faring better than most nations that had a significant Omicron wave.

Source:  Johns Hopkins data, via Google search.

 In Australia, for example, new case rates haven’t declined materially for about the past three weeks. Their current new case rate works out to be 81 / 100K / day.

In the U.K. new cases have begun rising again.  No clue whether that’s a fluke or the start of something new.  Their current new case rate works out to be 87 / 100K / day.

Canada (not shown) is currently around 16 / 100K / day, but declines have stalled.  New cases are actually up slightly in the past week.

Denmark and Norway (not shown).  Recall that they started their Omicron waves before the U.S., but just don’t even go there.  Cases are declining now in both countries, but the current rates work out to be about 350 / 100K / day in Denmark, and 230 / 100K / day in Norway.

In that context, in the U.S., with 18 / 100K / day and still falling fairly rapidly, things look pretty good.  Hope it keeps up for a while yet.

Post #1446: COVID-19 trend at William and Mary, new case rate finally peaks.

 

Source:  Calculated from the William and Mary COVID-19 dashboard

The new COVID-19 case rate at William and Mary finally appears to have peaked.  This week saw less than half the number of newly-diagnosed cases compared to last week.   The rate is still about 4.5 times higher than the rate observed in the 18-24 population of Virginia.

Based on the most recent email from the W&M administration, they are no longer going to do contact tracing.  (That is, identifying the close contacts of known new COVID-19 cases, and checking those close contacts for infection.)  This means that the new case counts moving forward will not be strictly comparable to the data so far, because they will no longer contain (e.g.) asymptomatic individuals who were only found via contact tracing.

That said, at this point, I don’t think anyone cares.  Almost everyone on campus is immunized, case counts are falling, and as far as I know there have been no reports of severe illness from Omicron.  As of yesterday, W&M lifted their mask mandate for indoor spaces other than classrooms.

What will the new normal be?

All of that seems consistent with the slow return to normalcy.  Let’s all be glad that Omicron is substantially less virulent than Delta, and that vaccines (and particularly, the third or booster shot) remain reasonably effective at preventing severe illness.  All told, those changes bring COVID a lot closer to being “flu-like” in terms of health risks.

Elsewhere, I’ve made the case that in most parts of the country now, a boostered adult faces no more risk of hospitalization or death from Omicron than from flu, in a typical flu season.  As Omicron case counts continue to fall, I think that an increasing share of the population will come to more-or-less the same judgment.

My best guess for endemic COVID is that it will be accepted the same way that flu is, unless a more virulent strain arises.  Those who care will get a flu shot and a COVID shot every year.  Those who don’t, won’t.  Maybe wearing masks in flu season will become socially acceptable, as it is in much of Asia.  (I, for one, hope that’s true, now that we’ve woken up to the realities of aerosol spread of disease.)

As with flu, we’ll probably see a wintertime peak in COVID-19 activity in the Northern Hemisphere, because that’s the pattern for coronaviruses in general, and (so far) COVID-19 in particular.

Here’s flu, from the CDC:

Here’s a collection of coronaviruses other than COVID-19, from the source cited below:

Source: Potential impact of seasonal forcing on a SARS-CoV-2 pandemic DOI: https://doi.org/10.4414/smw.2020.20224 Publication Date: 16.03.2020 Swiss Med Wkly. 2020;150:w20224 Neher Richard A., Dyrdak Robert, Druelle Valentin, Hodcroft Emma B. Albert J.

All of that would make sense, I think.

Blitz-demics.  The only thing that doesn’t quite make sense in this COVID-as-flu scenario is the effect of the extremely high contagiousness of COVID-19 relative to flu.  Typical seasonal flu has an R-nought of about 1.3 (per this scholarly reference).  Pandemic flu outbreaks such as the 1918 flu have an R-nought of perhaps 1.8 (same reference).  But Omicron (B.1.1.529) has an R-nought of about 15, and son-of-Omicron (BA.2) is about a 22.

In other words, where the average person with flu might go on to infect 1.3 to 1.8 others, absent any interventions, the average person with Omicron would infect 15 others, absent any interventions.

The upshot of that is that if immunity fades over time (and it does), when there is an outbreak of Omicron, it’s going to spread far faster than flu.  In round numbers, you’d have to guess about 10 times as fast, given that the R-nought is about 10 times as high.

This is a particular issue for “congregate living situations”, such as prisons, nursing homes, ships, barracks, and dorms.

You may or may not recall that early in the pandemic, COVID-19 swept through many U.S. prisons before anybody even thought to do anything about it.  It disabled the U.S.S. Theodore Roosevelt, again before anyone even considered any effective means to contain it.

I suspect that will become part of the new normal with endemic COVID-19.  As population immunity wanes, we’ll end up with “blitz-demics”, for want of a better term.  An outbreak of Omicron (or its successor) will run though a prison, campus, ship or workplace before anybody’s even really aware that there’s an issue.

But all of that — if it comes to pass — is a problem for the future.  Right now, things look better in the U.S. than in much of the rest of the world.  All we can do is hope that current U.S. trends continue.

Source:  Johns Hopkins data, via Google search.

Post #1445: COVID-19 trend to 2/28/2022

 

I think we’re rapidly approaching the end of the Omicron wave in the U.S.  I’ll define that as the point at which the daily count of new cases stabilizes at some low “endemic” rate.  It’s tough to say that, exactly, as the Presidents’ Day data reporting messes up today’s estimate of the new case trend.  Despite that, that’s how it looks to me.  We’ll have a better fix on that tomorrow.

As of 2/28/2022, the U.S. stands at 22 new COVID-19 cases per 100K population per day.  That’s the same as it was as of last Friday’s data, and it’s only down 11% in the past seven days.  But, as noted above, part of that is an artifact of getting past the lack of data reporting on Presidents’ Day.

That said, everything I can see points to a sharp slowdown in the rate of decline of new COVID-19 cases in the U.S.  Ready or not, I think we’ll soon know what our endemic level of Omicron looks like. Continue reading Post #1445: COVID-19 trend to 2/28/2022

Post #1441: COVID-19 trend to 2/22/2022

 

The Presidents’ Day holiday interrupted COVID-19 data reporting, so there was no usable update yesterday.  Today, as of 2/22/2022, the U.S. stands at roughly 26 new cases per 100K population per day, down 40% in the past seven days, and down 90% from the peak of the Omicron wave five weeks ago.  If there is any reduction in the rate of decline, it’s pretty subtle so far.

There are a couple of other things worth noting.

First, for the U.S., son-of-Omicron (BA.2) appears to be a dud.  In theory, it’s about half-again as infectious as the original Omicron variant (B.1.1.529), and should be displacing the original variant.  In practice, the CDC keeps revising its estimates of spread of BA.2 downward.  As of the week ending 2/19/2022, BA.2 was still estimated to account for less than 4 percent of all new U.S. cases. 

At the current rate of decline of new cases, I’d guess that the Omicron wave will be well and truly over before BA.2 can even get going.

Second, hospitalizations and deaths have not fallen anywhere near as fast as new cases.  That’s completely different from the end of the Delta wave, where those fell in sync.  The upshot is that the case hospitalization rate for Omicron is now back up to where it was under the far-more-virulent Delta.  That’s puzzling, and I keep thinking that there has to be some significant explanation for it.

I’ve fumbled around trying to explain it.  Maybe it’s cases missing out of the official counts, due to the rise of home testing.  Maybe more virulent strains of Omicron are gaining ground.  But neither of those really explained the magnitude of the effect.

Michael Andreas, a long-time reader of this blog, provided what I think is the most plausible explanation of this:  Maybe immunity is waning among the elderly.  They were first in line to get vaccinated and boostered, they should be first to see that vaccine-provided immunity decline.  And because they are so much more likely to be hospitalized or die from COVID, compared to others, a shift in cases toward the elderly would markedly increase the number of hospitalizations and deaths per case.

Tracking down the numbers by age, the end of the Omicron wave has, in fact, been associated with a shift toward the elderly in terms of new cases, hospitalizations, and deaths.  Plausibly, that’s the result of waning immunity in that population.

Case trend

Data source for this and other graphs of new case counts:  Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 2/23/2022, from https://github.com/nytimes/covid-19-data.”  The NY Times U.S. tracking page may be found at https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html

From the second graph, you can see that there is still no clear slowdown in the rate of decline in new cases for the U.S. as a whole.  We’re approaching our one-month anniversary of cases declining at a steady 40+% per week.

Maybe there’s the start of a slowdown showing for the states that led the decline.

Son-of-Omicron remains a dud in the U.S.

Source:  CDC COVID data tracker.

Recall how COVID strains are named.  The two original strains of COVID-19 were termed A and B.  Each generation of variants is separated by a dot.  Each new variant is numbered in the order it is discovered.  And then, after four generations, you give that line its own letter designation, if there are any further sub-variants.

The original strain of Omicron is B.1.1.519.  That was given the alias BA.  Then BA.2 is the second known sub-variant, dubbed son-of-Omicron.  And then there’s BA.1.1, which is the first grandson of Omicron, so to speak.

BA.2 is thought to be half-again more contagious than the original Omicron strain.  It has (e.g.) become the dominant strain in Denmark.

But in the U.S., it’s spreading far less rapidly than was originally projected.    The CDC’s current estimate (for the week ending 2/19/2022) is that it accounts for 3.8 percent of all new cases.  That’s actually down a bit from where the CDC thought it was last week.  So this is spreading far less rapidly than the CDC had projected.  There now seems to be little danger of it prolonging the U.S. Omicron wave, given how fast cases in general have been falling.

The only thing happening at the moment is that the original Omicron strain is being pushed out by BA.1.1.  Near as I can tell, nobody seems to think this has any clinical or epidemiological significance whatsoever.  There is no research to suggest that grandson-of-Omicron BA.1.1 is materially different from the original Omicron B.1.1.529.

Are rising case hospitalization and mortality rates due to waning immunity in the elderly?

Source:  Calculated from CDC COVID data tracker data, data accessed 2/22/2022.

On the downside of the Omicron wave, we’ve seen a far faster rate of decline in new cases than in hospitalizations or (two-week-lagged) deaths.  The result is that the case hospitalization rate for Omicron is back to where it was under the far-more-virulent Delta variant.

I seem to be the only person in the U.S. who thinks that needs some sort of explanation.  Taken at face value, Omicron appears to have grown far more virulent as the cases have declined.  But surely if that were true, somebody would have noticed it.

I’ve thrown a couple of possible explanations at this, but nothing really stuck.  Maybe a rapid growth in home testing has significantly reduced the trend in officially-counted cases.  But the reduction in cases needed to account for a tripling of the case hospitalization rate is just too large to be plausible.  Maybe this is due to the newer strains of COVID-19 (BA.2 and BA.1.1) being more virulent that the original (B.1.1.529).  But nobody says that about BA.1.1., and BA.2 accounts for far too few cases to matter yet.

Michael Andreas, a long-time reader of this blog, suggested what I now think is by far the most plausible explanation:  Waning immunity.  In particular, waning immunity among the elderly who a) were first in line to get vaccinated and boosted, and b) are far more likely to be hospitalized or die, if infected, compared to the remainder of the population.

First, it’s well-established that immunity from COVID-19 infection declines over time, whether from vaccination or from prior infection.  Prior to Omicron, the debate over booster shots centered on this observable decline in immunity, particularly among the elderly.  Some of the estimates of decline in immunity were remarkably large, as in this this study of persons using Veterans Administration facilities, a largely elderly population.  Other studies significantly slower rates of decline.

Source:  Figure 1, SARS-CoV-2 vaccine protection and deaths among US veterans during 2021, Barbara A Cohn et al, Science, Vol 357 no. 6578,

Just to underscore how concentrated those severe outcomes are, here’s a repeat of a graph showing the case mortality data for COVID-19 and flu. For either disease, almost all the deaths occur among the elderly.

(There’s nothing unique about flu or COVID-19 in this regard.  If you graphed all-causes mortality, or the most common causes of death, you’d see something very much like this.  Other than deaths from accidental causes, the sole exception that comes to mind, among major causes of death, is breast cancer, where roughly 40 percent of deaths are in the under-65 population).

And so, putting the argument together, the elderly:

  • are at highest risk for loss of immunity over time,
  • were vaccinated and boostered first, and so have had the greatest time elapse since immunization, and
  • have vastly higher case hospitalization and case mortality rates compared to the rest of the population.

And, sure enough, as of mid-February 2022, COVID-19 deaths have become ever-more-concentrated in the elderly.

Source:  Courtesy, Michael Andreas, source data are Provisional COVID-19 deaths by week, sex, and age, from NCHS. 

So it’s not as if the virulence of Omicron has increased across-the-board. It’s that the elderly — and only the elderly — appear to have lost some of their protection against dying from COVID-19.

We see a similar but more muted change in hospitalizations.  The elderly’s share of new COVID-19 hospitalizations has been rising for roughly the past month and a half.

Source:  Calculated from the CDC unified hospital dataset, accessed 2/23/2022.

As far as I can tell, there’s no way to get reliable national information on cases by age in a timely fashion.  Instead, I’m using data from Virginia, and using only the period of time following their recent clean-up of cases with unknown ages.

The results from Virginia reinforce what you’re seeing above.  The elderly’s share of all new cases has been rising fairly rapidly during the decline of the Omicron wave.

Source:  Calculated from Virginia Department of Health file of total COVID-19 cases by age group.

This is a little bit piecemeal, but taken as a whole, the evidence suggests that the elderly’s share of new cases, new hospitalizations, and deaths is rising. 

That is particularly notable given the return to school that occurred under Omicron.  If anything, we’d have expected cases in the pediatric and young-parent age groups to increase as a fraction of the total.   To the contrary, what we’re actually seeing is a risking fraction of all cases and severe cases in the elderly.

There is no way directly to prove it, but the most plausible explanation is that immunity is waning first among the elderly.  And that’s why we’re seeing what looks like an increasing (non-age-adjusted) case hospitalization and case mortality rate at the end of the Omicron wave.  Because hospitalizations and (particularly) deaths are so concentrated in that age group, even a modest shift in toward older persons can plausibly result in a marked increase in the rates per case.

I haven’t take this to the final conclusion step yet, to see if I can reconcile all the numbers based on the higher case rates of the elderly.  But, back-of-the-envelope, the shift in age mix of new cases from Virginia, combined with the extreme concentration of deaths in the elderly, does seem to be able to account for the much slower decline in deaths compared to cases.  As the share of cases in the elderly roughly doubled, all other things equal, we should expect to see a near-doubling of the case mortality rate.  And that’s exactly what we’ve seen nationally, from 0.3% of cases to 0.6% of cases.

The upshot is that this seemingly modest demographic shift is probably adequate to explain the rising case mortality rate, and so, probably the rising case hospitalization rate as well.

As a result, the most likely explanation I can find for the apparent uptick in case hospitalization and mortality rates is that immunity is declining more rapidly among the elderly, right now, than it is in the rest of the population.

Obviously, this has some fairly serious implications if you happen to be elderly.  Hardly a day goes by when I don’t read some comment, on some newspaper article, that boils down to “I’m vaccinated and boosted, so I no longer need to wear a mask.”  That attitude could be a costly mistake for an elderly person if immunity is now rapidly declining.

Given that it’s the CDC’s job to make recommendations on mask use and vaccination, it would be helpful if someone in a position of authority there would directly address this.  What I see, as I peruse the CDC website, is reticence to provide detailed information on the loss of vaccination-based immunity over time.  But if we’ve got a bunch of older Americans who think they’re good to go because they got the booster, the CDC should be burdened to clarify just how much protection the average older American can expect to have, some months after that last booster shot.

Post #1440: William and Mary COVID-19 trend to 2/21/2022: Still moving in the wrong direction.

 

Source:  Calculated from William and Mary COVID-19 dashboard.  Virginia data were extrapolated from the most recent (2/18/2022) data by age, from the Virginia Department of Health.

For the past week, William and Mary saw an average of 15 newly-diagnosed COVID-19 cases per day.  That’s an increase compared to last week, and that now works out to be about seven times the rate of new cases in the 18-24 population of Virginia as a whole.

Plausibly this is not a serious threat to health, given the generally milder nature of Omicron, and given the generally high rates of vaccination and boosters among the student population. Plausibly.

That said, it’s hardly something to be proud of, and we appear to be under-performing relative to peer schools in Virginia.

Above are large (5000+ enrollment) Virginia colleges and universities with at least some on-campus residences, showing the rate of new COVID-19 cases per nominal total enrollment for the past week.  (These enrollments figures all exceed actual on-campus enrollment to a larger or smaller extent, including the number for William and Mary).

Even though this isn’t the cleanest of comparisons, it shows you that, on paper at least, of all the major residential colleges and universities in Virginia, William and Mary now ranks first in COVID-19 incidence. 

In fairness, there is a lot of variation in what’s being reported in the table above.  Not every comparison is a proper apples-to-apples comparison.  That said, for the ones that should be close to correct — e.g., U.Va — disease incidence at William and Mary looks to be out-of-line with our peers.

Probably not a huge cause for concern, all things considered.  But certainly nothing to be proud of, either.