The U.S. is now 40% below the peak in new COVID cases/ 100,000 /day.
Source: Calculated from NY Times Github COVID data repository, data reported through 1/30/2021. Continue reading Post #986: Current trend: Would it help if I blamed the Acme Corporation?
Source: NY Times Github COVID data repository, data reported through 1/29/2021.
Above: National data (thick line) and six regions, seven-day moving average of new COVID-19 cases / 100,000/ day. Top graph is in “natural units” (i.e, actual COVID case counts per 100,000 per day). Bottom graph is in logs. The main reason for using logs, in this case, is that a constant rate of growth graphs as a straight line.
When things get this boring, you really have to dig to find something to write about. In this case, it’s that the rate of decline in new cases / 100,000 / day appears to be more-or-less constant.
So: Paint is drying uniformly. Not exactly prime click-bait, but it’s the best I could come up with.
Continue reading Post #985: Trends update: Like watching paint dry
Source: Calculated from NY Times Github COVID data repository, data reported through 1/28/2021.
I’m going to do one more post on herd immunity and vaccination. But this is a very positive post. The point is, vaccinations at the current rate should vastly speed up the end of the U.S. third wave of COVID.
That’s really not obvious, is it? Conventional wisdom is that vaccinations will help us get this under control many months from now. But that conventional wisdom springs from a fundamental misunderstanding of herd immunity. It springs from the thoughtless repetition of “70% required for herd immunity”,without realizing that’s for herd immunity in isolation, with no other COVID hygiene measures in place.
By contrast, as long as we continue masking/distancing/limiting, infections alone have already brought us near or past the point of what I call “remission” herd immunity. (See e.g., Post #982). The fraction of the population that is immune via infection is roughly enough to drive the viral replication factor (R) below 1.0. Again, as long as we continue masking/distancing/limiting.
The implication is that newly-vaccinated individuals aren’t moving us slowly in the direction of some far-off target. They are moving us well past the level required to get viral replication below 1.0. Right now. And though the magic of leverage and compounded growth rates, every percent of the population immunized has a huge impact on the speed at which the third wave recedes.
How huge? Roughly speaking, at current rates, by my calculation below, day-for-day. We’re currently vaccinating about 1M per day. Every 3M persons vaccinated brings the date of the end of the third wave forward by roughly three days.
All bets are off once the new COVID-19 variants become prevalent. But my contention is that we can get the existing variant under control in short order, just by maintaining COVID hygiene and maintaining the current rate of vaccinations.
Details follow. Continue reading Post #984: Herd Immunity V: Rapid end of the U.S. 3rd wave of COVID via vaccination.
Sometimes, boring is good. Don’t know about you, but I could settle for some boring right about now.
All data for this post are from the NY Times Github COVID data repository, data reported through 1/27/2021.
US rate of new cases / 100,000/day is back to pre-Thanksgiving levels. Things aren’t quite as uniform across states as they were a few days ago, but most continue to show a downward trend.
Continue reading Post #983: A boring update on recent COVID trends.
Judging from the feedback I’ve gotten, most people can’t make head or tail out of my last three posts on herd immunity. (Post #978, concept; Post #979, empirical estimate; Post #981, U.K. variant estimate).
At my wife’s suggestion, let me just tell it as a story, and see if that’s clearer.
You’ll hear that 70% of the population must be immune to COVID-19 before we can end the pandemic in the U.S.
That’s wrong. Or, at the very least, that depends on what you mean by “end”.
By “wrong”, I don’t mean that there’s some uncertainty around that number. There is, to be sure. But by “wrong”, I mean the 70% figure is conceptually wrong.
If we’re talking about the problem we are facing right now — ending this current wave of the pandemic — then that’s the wrong number to look at. It’s far too high. And that’s because most people who use that 70% figure don’t have their thinking straight about what, exactly, that 70% number represents.
And, ironically enough, clarifying that last point was what those confusing posts were about. So let me try to fix that with this post. Continue reading Post #982: Herd Immunity IV: The simplified version.
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:
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.
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.
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.
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 trajectory. As 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
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
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:
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.
