Post #981: Herd immunity III: Which states are U.K.-COVID-proof

Source:  U.S. National Park Service.

Edit:  Read Post #982 first.

This is a short post for those who have been following along.  If you haven’t been following along, you should probably go back and read the last two posts on herd immunity.

If nothing else, this post illustrates why somebody needs to do this calculation with full accuracy.  Because, when you get down to it, being able to answer the question below, accurately, seems kind of important.

There’s a new, more infectious COVID variant on the loose in the U.S., commonly termed the U.K. variant.  In this post, I’m going to redo the calculation Post #979, substituting an estimate of the U.K. variant’s viral transmission rate for the previously-assumed 3.33 R-nought (R0 ) value for the existing strains of U.S. covid.

The results will tell me whether any U.S. states have enough “herd immunity” to be have COVID new case rates continue to fall, even as the U.K. variant becomes the dominant COVID variant in the U.S.

The U.K COVID variant is rumored to raise the effective viral transmission rate from roughly 1.1 to maybe 1.5.  That means R0 should rise proportionately, or:

  • R0 (U.K.) = 3.33 x (1.5/1.1) =  4.54.

Now plug that into the required-herd-immunity-level equation from Post #979.  Below, 0.53 is the estimate effect of current masking/distancing/restricting actions.  Solve for the effective herd immunity level He that will produce an effective viral transmission rate of 1, with the U.K. variant.

  •  4.54 * (1 – (H + .53 – .H*.53) = 1.0
  • Solve for H
  • H =~ 0.54

Based on this rough calculation, any state where more than 54% of the population is immune will be protected from this new variant by the combined effect of the population (herd) immunity and the continuation of all other existing efforts to disrupt virus transmission (masking/distancing/restricting).

Look back to Post #958 to see a reasonably current list of states by estimated proportion of population that has already been infected.  Although this is a little old, and ignores vaccinations, it gives you a rough cut.

Prior to the onset of vaccinations, just three states exceeded that level.

I hear that North Dakota is nice in the summer.

Post 980: The French ban the worst masks.

European policy regarding masks seems to remain months ahead of the U.S. 

In prior posts, I documented that Germany has been distributing FFP2 (N95-equivalent) masks to high-risk populations since 12/15/2020.  The obvious analogy for U.S. heath care policy would be for the Biden administration to offer N95s to the elderly via Medicare. 

And both the country of Austria and the state of Bavaria are requiring high-filtration masks in public places. Continue reading Post 980: The French ban the worst masks.

Post #979: The two distinct levels of herd immunity, Part II

Edit:  Read Post #982 first.

This post presents a calculation to match the herd immunity discussion of the just-prior post.  Read Post #978 first, then this one.

Here, I back-solve for the level of immunity in the population that should bring the effective COVID-19 viral reproduction factor below 1.0 (i.e., end the third wave of the pandemic), as long as we maintain masking, distancing, and other behaviors limiting viral spread.

This is a simple calculation, based on one point in the progress of the pandemic in North Dakota.  That point being the two weeks when North Dakota saw its sharpest increase in cases.

So there’s not a lot of accuracy here.  And it’s not an estimate, in the sense of being a statistic calculated from pooling a lot of data.  It’s really just a round-numbers (but data-based) illustration.  It shows that the two different herd immunity concepts defined in the prior post lead to two very different levels of required population immunity.  And that we may already be hitting the lower level in some states.

Bottom line:  40%.  Once something like 40% of the population has been infected, that ought to be enough to set the third wave of COVID on a downward trajectoryAs long as we maintain masking, distancing, limits on social gatherings, and other such controls.   But we’d still need the classic “70% herd immunity” to return to normalcy, meaning, life without those controls.

The upshot is that the uniformly downward trajectory seen in the U.S. Midwest probably isn’t a fluke, or luck.  It’s probably just a matter of arithmetic.

The clear policy implication is that there is a more efficient way to use the COVID vaccines, if the goal is to bring the U.S. third wave of COVID to a close.  You should concentrate vaccination in those states that have had the fewest infections so far.   You shouldn’t aim for an equal share of the population vaccinated in each state, as we are now.  You should aim for an equal share immune in each state, either via vaccination or via prior infection.  That means shifting vaccine from states that have already had widespread COVID infection, to states where a higher fraction of the population still lacks immunity to the virus.

Continue reading Post #979: The two distinct levels of herd immunity, Part II

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.