Author: chogan@directresearch.com

Post #978: The two distinct levels of herd immunity, Part I

Edit:  Read Post #982 first.

I think this is an important post.  So, no kidding around. Minimal entertainment value.  And you’re going to have to follow a little bit of arithmetic in the followup post.

And at the end, you’re going to say, well, that’s obvious.  And yet, nobody seems to have grasped this.  Yet.  Or, at least, I have yet to find a single discussion that makes this point.

The point being that there are two distinct herd immunity levels that matter.  One is the fraction of the population that needs to be immune, to stop a pandemic, if immunity is the only tool used to limit spread of the virus.  That’s our classic “70% required for herd immunity”.  The other is the level of immunity needed to stop a pandemic while all the other infection limiting tools (masking, distancing, limits on gatherings) are still in place.  That’s a much lower limit that I have not seen discussed anywhere.  But that’s the level of immunity that’s relevant to ending this third U.S. COVID wave.  And I crudely estimate that second version of herd immunity to require something like 40% of the population to be immune.

That’s a little controversial, I think.  Or, at least, under-discussed.

So here goes.  Words today, crude numerical estimates tomorrow. Continue reading Post #978: The two distinct levels of herd immunity, Part I

Post #977: “Wear an N95” goes mainstream

September 9, 2020

 

 

 

January 24, 2021.

 

 

Above:  Fraction of the population wearing masks when in public.  Source:  Carnegie Mellon University Delphi Group COVIDCast.

By this time, most U.S. residents seem to have gotten the memo about wearing masks.  And my reading of recent news coverage is that America now seems ready to up its game on masks.  And it’s about time.

If you’ll go to Google News and search for N95, you’ll now see a spectrum of articles on a) why you should wear an N95, b) where to get an N95, c) alternatives to an N95.   As well as articles telling you to wear two masks, if you can’t get an N95.  Or articles giving reasonably useful generic ratings of which masks are better than others.  Or introducing you to other high-filtration standards, such as the Korean KF94.

Among which is an op-ed in today’s Washington Post with the straightforward title:

Everyone should be wearing N95 masks now

The Washington Post op-ed itself is pretty good.  The comments below it are just pitiful.  Either that was a target of the Russian trolls, or Americans have a long was to go in terms of getting educated about masks.  I don’t think I’ve seen misinformation and disinformation so heavily concentrated in one place before.

In this post, I’m going to offer three bits of perspective on how far we’ve come on this issue of wearing N95 masks, and then summarize any new practical advice that I can glean from today’s  crop of articles.

In short:  We’ve gone from “you don’t need one, and you shouldn’t wear one”, and no federal leadership on the issue, to “you need one to avoid aerosols, you should find one wherever you can”.  And still no clear Federal leadership on the issue.  And still a hard time figuring out how to buy a true N95 mask.

This is an area where the Biden administration could make a real difference in ordinary citizen’s lives.  Reading those Washington Post comments, I’d say that pretty much everybody recognizes how hard it is for a citizen to buy an N95 mask and have confidence that it is the real article.   It’s not like that’s some secret.

So, anything from cleaning up the marketplace so that we could know what we are buying, to some sort of government-run certification program so we could know what we are buying, to outright provision of certified N95 masks.  Starting, as I’ve suggested earlier, with provision of N95s to the elderly via the Medicare program.

 

Continue reading Post #977: “Wear an N95” goes mainstream

Post #976: Simple projection to March 1, and herd immunity.

How close will the U.S. be to herd immunity for COVID-19, on March 1 2021?  Even with the significant uncertainty involved, it’s worth making a few simple projections of that.  If nothing else this will put the current vaccination effort into perspective.

Even under a rosy scenario where vaccine injections double from the current 1M/day, and new infections continue to fall, only about half the population will be immune to COVID-19 as of the start of March 2021.  That’s well below the 70% that was thought to be required for herd immunity under the original strains of COVID, let alone the higher percentage that will be required for the more infectious U.K. strain.

Why does March 1, 2021 matter?  If the U.S. COVID third wave truly has crested, our next test will come as the more-contagious U.K. variant becomes the dominant U.S. COVID strain.  That’s predicted to happen sometime in March 2021.  Near as I can tell, that prediction is based solely on the amount of time it took for that strain to become dominant in the London area.  So that amounts to a crude guess.  But, at present, that’s the only guess we’ve got.

And if that’s correct, then vaccinations should proceed as quickly as possible.  But under any plausible scenario, vaccination alone won’t prevent a fourth U.S. wave of COVID-19.  We really need to be thinking about what else we’re going to do — such as making N95 masks available to citizens — in addition to vaccinations.

Details follow.

Continue reading Post #976: Simple projection to March 1, and herd immunity.

Post #975: Nobody knows how much COVID vaccine the U.S. has?

Today, a headline on CNBC states:

CDC director says federal government does not know how much Covid vaccine the U.S. has

I’m shocked, shocked to hear that. 

Well, actually, I’m not.  I called this one back in June 2020 (Post #732). Which I will now quote.

We can also expect that vaccine distribution will be done with the current administration’s hallmark lack of transparency.  The usual talking-out-of-both-sides-of-their-mouths.  The usual contradictory statements by various officials.  The usual lack of not merely accountability, but basic accounting.  I’d say, based on prior behavior, that something as obvious as a simple list of which states got how many doses will not be made public.  At the time when it really matters — this fall — I’d say the odds are excellent that we (the US people) won’t even know where the vaccine is.

Continue reading Post #975: Nobody knows how much COVID vaccine the U.S. has?

Post #974: Today’s trend update, and maybe one more lesson from the French

Source:  Calculated from NY Times Github COVID data repository, data reported through 1/24/2021.

Just another boring post.  Thank goodness.

  • The COVID-19 new case rates continue to fall.
  • They are falling in more-or-less every state.
  • It’s not slowing down yet.  The case counts continue to fall at a constant percentage rate.  (It looks like it’s slowing down, above, because the thick blue line is starting to bend a bit.  But a graph like that doesn’t show the growth rate.  I’ll graph it on a log scale, below, to show the constant growth rate.)
  • It’s falling in more-or-less every state with more-or-less the exact same growth rate.  That’s a point that deserves further discussion.
  • Finally, Virginia’s curve now shows the predicted “speed bump” (Post #964).  The rate has begin to drop abruptly as the seven-day moving average passes the “lump” of cases reported circa 1/17/2021.

Continue reading Post #974: Today’s trend update, and maybe one more lesson from the French

Post #972: The rain falls on the just and the unjust.

Source:  Calculated from NY Times Github COVID repository data.  Data reported through 1/23/2021.

U.S. new case counts are down to where they were before Thanksgiving.  And they are falling in all 50 states and DC.  That’s the only solid takeaway from this posting. The rest is just an explanation of why that’s so annoying. Continue reading Post #972: The rain falls on the just and the unjust.

Post #971: Update to British COVID variant post #956, six more states

And now updated to mid-day 1/22/2021:  Four more states, to a total of 26.

References for  today’s additions

Massachusetts

New Jersey

Oklahoma

Tennessee

Prior post,  22 states have at least one case.  Not clear that it’s actually spreading that fast, as states may now be finding it because they are looking for it.  That said, it’s not going to be long before it’s been found more-or-less everywhere.

References for today’s additions:

Illinois

Louisiana

Michigan.

Oregon

Utah

Wyoming

 

Original post,  Post #952, 14 states had at least one case.

Post #970: Tempus fugit and the long right tail of the virus.

Above:  Nine days ago versus one day ago (data through 1/21/2021).  Calculated from data via NY Times Github COVID data repository.

The trend is down, for the U.S. as a whole, and for almost every state.  That’s not news if you’ve been following along.

The national rate at the top of this post is moving sharply downward mainly due to behavior in a few large states, particularly California (left, below). Helped by New York (right, below).

But in the median (typical) state, there’s  a downward trend, but it’s anything but sharp.  And what I have noticed lately is that North Dakota seems to be “asymptoting”, for want of a better verb.  It’s not plunging toward zero cases.  Instead, the rate is slowly drifting down.  Just today, their seven-day moving average finally crossed below 20 cases / 100,000 / day.

In fact, for the Midwest as a whole, if you compare the pace at which the rates went up (left side of graph) to the rate at which they are doing down (right side of graph), the pace of reduction appears slower almost everywhere.

If the Midwest is the harbinger of the third wave, then what we look forward to is a prolonged period of elevated but slowly-declining rates of COVID.  Not crisis levels.  But not disappearance of the disease either.  If this were a statistical distribution, we’d call that a “long right tail”.  And it looks like we’re moseying toward that with COVID.

That’s unfortunate, given that we’re kind of in a race with the more contagious UK COVID variant.  But it is what it is.

My already-stated belief is that this is the start of the end of the U.S. third wave of COVID  That said, it looks to me like we’re heading for a long right tail.  With the UK variant still in the background.

Post #969: Political affiliation: Vaccine irrationality and its side-effects.

Every once in a while I stumble across separate pieces of seemingly-true data that make me question my own sanity.

When in fact, I should be questioning the sanity of others.

 

As I have noted before, flu vaccine is only about 60% effective in the best years.  Most years, it’s not even that effective.  (The graph on the left is from the U.S. CDC).  Flu rarely kills anyone other than the frail elderly, and has a case mortality rate of about 0.1% in a typical year.*  For most people, flu is a nuisance.  And most people have some degree of native immunity against some prevalent strains of flu, every year.

* That’s flu as cause of death, divided by flu “cases”, that is, people who were formally diagnosed with flu.  And that’s really the only hard number that exists, in this regard.  If you see somebody citing something else, either they’re making it up, or they are using a denominator that is something other than diagnosed cases.

In short, with flu vaccine, we’re talking about a modestly-effective way to reduce the odds of catching a mostly-harmless short-lived disease.  That you might not catch anyway, because you already have some of the right antibodies.

By contrast:  The COVID-19 vaccine is being touted as 95% effective.**  COVID kills a lot of people, and so far in this pandemic the U.S. case mortality rate rate is (400,000 / 24,100,000 =) about 1.6%.**  And near as we can tell, nobody has native immunity to COVID.

** As discussed in earlier posts, the COVID effectiveness can’t be directly compared to the flu effectiveness.  For COVID, that’s the effectiveness at preventing severe, symptomatic infections.  They don’t actually know how good the vaccine is at preventing infection in total (including mild and asymptomatic infection), because they didn’t draw blood and test for antibodies.  By contrast, the flu figure is the effectiveness at preventing all infections, as evidenced by presence of any antibodies to flu in the blood, whether or not flu symptoms were present.

*** See note above.  Anybody who cites a vastly lower number is either making it up, or using some other denominator such as an estimate of all infections.  In which case, the number would not be comparable to the 0.1% case mortality rate for flu.  You see a lot of disinformation based on apples-and-oranges comparisons between some putative “all infections” mortality rate for COVID, and the standard case mortality rate for flu.  That’s not a valid comparison.

So, COVID is more dangerous, the COVID vaccine is more effective, and fewer people have any immunity to COVID.  Compared to flu.  Those appear to be the facts.

And so, rationally, shouldn’t you be more willing to get the COVID vaccine than to get the flu vaccine?  I mean, maybe you just dismiss all vaccines.  OK.  But for the more rational part of the population, shouldn’t you be more likely to get the COVID vaccine than the flu vaccine, given the facts?

Nope.  Not if you’re Republican.

Here are results from two seemingly accurate national surveys.  And I note that the COVID question specifically phrased it as “determined to be safe by scientists and free to everyone”.  And that the December numbers were higher than estimates from September.  If you were to have asked in September, Republicans were far less likely to say they’d get the COVID vaccine than the flu vaccine.

For four-out-of-ten Republicans, getting vaccinated is off the table.  No matter what.  Not if the vaccine is guaranteed safe.  Not if it’s free.   You literally can’t give it away to that crowd.  Not even while the Republican POTUS is (incorrectly) taking credit for having developed the vaccine.

I’ve made up my mind, don’t confuse me with the facts?  That’s pretty much how I read this.  If that’s the attitude, then I guess there’s no arguing with it.  It is what it is, and it’s not going to change.  No matter what.

Luckily, screw ’em, we don’t need them.  They’re irrelevant.  Above is a modified version of the herd immunity calculation presented in a recent post.  The upshot is that if people simply follow through with their intentions, given the current state of the world, we’ll still exceed the 70% level required for herd immunity. And, as long as the limiting factor is the shortage of vaccine, it makes no difference that more than 40% of Republicans refuse to be vaccinated.  We’ll get there in the same amount of time, regardless.

So, ultimately, my take on it is, let them be ignorant.  It doesn’t do the population as a whole any harm, assuming that the overall amount of vaccine available is the limiting factor.  And assuming that 70% is the herd immunity level. (And that the vaccine literally prevents infections, including asymptomatic and mildly symptomatic infections, something that has not yet been shown.)  Even if we achieved no more herd immunity via infections, Republican intransigence on COVID vaccination is irrelevant.  We have enough rational people on both sides of the aisle to resolve this without them.