The best case would be R < 1 and herd immunity >70%.
R is the reproduction number, the number of cases that one case causes. R0 is the basic reproduction number, which is an idealization of how a disease spreads in a given population. Reff is a measured number for a particular situation. In looking at the models, I see R0 being used in ways that look like it contains other parameters as well. So I will just use R, which is the same as Reff. Using it without a subscript and the context will, I hope, indicate that it is totally situational.
The basic reproduction number can be taken to be inherent in a disease. Because populations differ, R0 is likely to show a range. A mathematical relationship can be derived between R and herd immunity.
The figure comes from an article that has many useful things about it, but not its web address. I found it through Google, and the address requires a token that times out. Here’s the header:
ETA: Here’s a link. Thanks, Scott!
The point of social distancing is to decrease the number of interactions that can transfer the SARS-CoV-2 virus and cause disease. That brings down R. If R is less than 1, then the chain of transmission will die out. In that case, the herd immunity can be low. But we can’t do social distancing forever. It would be useful to understand how we might get to higher herd immunities.
One way is with a vaccine. A great many vaccines are being developed, and several have moved into clinical trials. The vaccines work in different ways, which is good for the potential of finding one or more that work. But 12 to 18 months is highly optimistic for having a vaccine widely available.
This thread summarizes some of the R values that have been attained with social distancing. King County, Washington, managed to get R down to a little over 1 with social distancing, as did many European countries.
An article from the Los Alamos National Laboratory calculates that the R0 for Wuhan is 5.7, with a 95% confidence interval of 3.8–8.9. That’s higher than other estimates. From the figure above, that R requires 70-90% immunity for herd immunity.
Where is population immunity now? The best way to test for this would be serological testing, which looks for antibodies in the blood. There is still a lot we don’t know about how immunity to COVID-19 works, and there are individual studies that are being magnified out of proportion by reporters. So let me be careful in what I say.
Usually the human body makes antibodies to a disease as the disease progresses. Those antibodies continue in the blood and are effective for varying amounts of time. Antibodies to influenza last for about a year, which is part of the reason why a vaccination against the flu is necessary every year. There is still a lot we don’t know about antibodies to SARS-CoV-2. I’m not going to argue about individual papers, which must be put into a larger context by people who know a whole lot more about immunology than I do. For now, I’ll assume that COVID-19 produces antibodies, and those antibodies protect against the virus for more than a few months.
The question then is how many people have been infected. There is some evidence that people may be infected and suffer only minimal symptoms or be completely asymptomatic. The only way to determine immunity, then, is serological testing. A serological survey in Germany found that 14% of the people tested had antibodies to SARS-CoV-2. Here are a couple of threads on the study.
Another way to estimate population immunity is to look at the number of cases, minus the deaths. From the Johns Hopkins database on the afternoon of Friday, April 10,
- US population: 329,450,000
- US confirmed cases: 475,749
- US deaths: 18,022
- Remaining: 457,727
- Percent of population: 0.13%
Let’s look at New York state:
- Population: 19,540,000
- Confirmed cases: 159,937
- Deaths: 7,067
- Remaining: 152,870
- Percent of population: 0.78%
Or New York City:
- Population: 8,623,000
- Confirmed cases: 87,028
- Deaths: 4,260
- Remaining: 82,768
- Percent of population: 0.96%
It’s not possible to know the numbers of people infected, but if 15% of cases are confirmed, that would give 6.4% immune in New York City.
None of these percentages comes anywhere near what is required for herd immunity. This is why developing a vaccine is important.
It also raises serious questions about how to reopen the country. Both RNA and serological tests will be necessary to find who is infected and who is immune. South Korea has used detailed tracking by cellphone app to find who may have been exposed. We have some hard decisions ahead of us.
And a government study shows that if we reopen the country now, it will be almost as if we had done nothing.
Cross-posted to Nuclear Diner
BGinCHI
But Trump said it’s a bacteria, Cheryl.
You spray Bactine on your face and clothes and voila!
CURED
dmsilev
LA County started a general-population serological study today. First batch will be 1000 people.
Another piece of the puzzle is figuring out whether it’s feasible to do large-scale contact tracing so that any hot spots can do focused quarantines rather than locking down an entire county or state. Google and Apple announced a joint effort to provide infrastructure to let local health agencies do contact tracing via people’s phones. Some tech details here; it looks like some care has been taken to preserve anonymity and privacy. There’s a statement down at the bottom of the second page from the ACLU saying that they’re cautiously optimistic, which all things considered is a ringing endorsement.
Cheryl Rofer
@dmsilev: Excellent! Thanks!
Mary G
At least the feds grudgingly agreed to keep paying for testing beyond today after enough people screaming about it.
Another Scott
Here’s the DOI for the “Herd Immunity – A Rough Guide” paper – https://doi.org/10.1093/cid/cir007
HTH!
Cheers,
Scott.
Brachiator
Sadly, this is probably good enough for Trump.
Excellent, sobering post.
And thanks to those who provided links for further reading.
jl
@dmsilev: California did have a large scale contact tracking program and self-quarantine program until a week before the SF Bay shut down, then was ended for counties with large outbreaks because, without any testing capacity, it got too large for countries with big outbreaks to manage. But from news reports, it has continued in counties with smaller number of cases. It has continued in Napa County for example.
So, the tracing program couldn’t work on its own, may not have prevented a shut down. But may well have made the shut down more effective, and may allow us to start opening up within a few weeks, not a few months.
I think your general point is that we have to rely on several imperfect measures and hope they add up to being good enough until effective drug treatments and vaccines are ready, and if so I agree with that.
Edit: tragic question that will never be answered is that if the US feds, and probably Trumpsters, had not botched getting tests out, could California have avoided an extreme shelter-in-place. The economic and human costs are enormous and they are very risky in terms of maintaining population health due to decay of delivery of care for non-covid conditions. I don’t want to even think about the issue, what if California had some testing capacity, could we have avoided the shut down, or postponed it, or allowed something less severe?
joel hanes
I’m afraid it doesn’t make any difference how we _should_ re-open the nation.
On some day in the next couple months, Trump’s negligible patience and attention-span will have run out completely, and he’ll announce that it’s over.
In some red states, the governments will duly drop the official restrictions. Idiots will rush to pack the re-opened bars and to attend churches and sporting events, and a large second wave of severe cases will predictably ensue three or four weeks later. Non-idiots who have the privilege of doing so will stay isolated, and do their best not to be part of that wave of infection.
In other red states, which never locked down at all, local hotspots in prisons and nursing homes will produce shocking local death tolls, and seed their local communities with many more chains of infection, overwhelming the local health-care system, and so those states will slowly approach the kinds of per-capita death tolls we’re seeing in New York and Michigan. This will contribute to the second wave.
In sanely-governed places, the governments will attempt to keep as many restrictions in place as can be tolerated until there’s a vaccine. Trump will bellow, and MAGAts will defy the orders and guidelines, but the sane who can will stay home. That, and cross-infection from the states with dumbass governments will make the restrictions even more necessary.
In the time before mass vaccination becomes possible, I expect that one or more of the therapies being tried will prove out to be effective. I feel pretty confident that the treatment regimes available in a few months will be able to reduce the mortality rate in places in which the health-care system is not overwhelmed.
Cheryl Rofer
@Another Scott: Thanks! Updated in the post.
p.a.
I will personally pay for a face-to-face meeting between Boris and donnie at this point. In a broom closet. Door closed.
glc
Just a reminder that we don’t have case numbers.
James E Powell
@p.a.:
Just five minutes, Worm your honor,
Him and me, alone
JPL
Up until a week ago you had to be 60 plus with symptoms or in the hospital to be tested, so there is no reliable data. GA tests were running with a 40 percent false negative which is higher than the national average.
lgerard
You have to love this account of trump whispering wacko Peter Navarro
NYCMT
There is no goddamned way the IFR is that low.
Roger Moore
It also shows the absolute insanity of trying to let the pandemic run its course so we can get to herd immunity. The level in NYC has been enough to push the local medical system to the brink of collapse, and that’s with all the mitigation efforts we’ve put in place. They can’t take a doubling of the number of cases, and letting the pandemic proceed with exponential growth until 70-80% of the population has had it would involve a lot more patients than that.
Cheryl Rofer
To the folks complaining about the numbers: I know. I’ve thought about writing a post about all the uncertainties in all the numbers.
I like to have rough and ready numbers that I know are rough and ready. The point of calculating a (probably very poor) immune fraction of the US and New York populations is to see how far we are from herd immunity. The answer is very far indeed. That’s what I’m looking for.
Matt McIrvin
Apparently Rush Limbaugh and, of all people, Victor Davis Hanson (remember him? why don’t these people go away?) are pushing the idea that most of California got asymptomatically infected in fall 2019 and already has herd immunity, as a way of not giving any credit to Gavin Newsom. This is why so many people are talking about having secretly gotten COVID-19 in the fall.
What strikes me is that it’s so easy to debunk. Where are the mass graves of Californians?
jl
@Cheryl Rofer: @Another Scott: Thanks for finding and posting that tutorial on herd immunity.
I think the two numbers Cheryl talks about are part of necessary conditions for reopening, but not sufficient. Also need to put in place programs to keep resurgence of disease down to isolated outbreaks, at least until effective treatment and/or vaccine is available.
I will run an idea by Cheryl and see it appeals to her inner chemical engineer. The basic qualitative problem is that with an R > 1, and no herd immunity, there are two equilibria in a simple random mixing model (and I think that is an OK approximation for covid-19): unstable equilibrium at zero prevalence and stable equilibrium at herd immunity level of prevalence. The trick of controlling diseases with R > 1 and no herd immunity is to find feasible controls that keeps society within a certain acceptable neighborhood around the unstable low equilibrium. We do this with several diseases now. So, I don’t think the covid-19 control problems is entirely new. We just have to find the gimmicks that covid-19 uses to cause trouble, and find a weak point in the gimmicks to leverage good control policies. We do it with TB for example.
My IMHO guess, is that, looked at as a control problem, covid-19 has a bad combo that society hasn’t had to deal with for 100 years: probability of a lot of asymptomatic transmission and quick high demands on health care system, which demands quick extraordinarily expensive and risky measures, such as population wide shelter-in-place policies. TB has more asymptomatic transmission, and as far as we can tell, R0 > 3, but initially TB infections have three types (IIRC): fast, slow and latent. So worse than covid-19 in transmission respect, but we get a break in that the bad health consequences are on average slower, so that bought control people time. But, after WWII in some parts of the country, there were enough people with fast infections that they were falling down sick and needed emergency care, and in some places, quick temp sanitoriums and clinics had to be built.
joel hanes
@JPL:
there is no reliable data
… and there may never be any reliable data for this phase of the infection except from places such as Scandinavia, Finland, New Zealand, and Germany — places with adult leadership.
As long as Trump remains in office, we’ll never get the needed testing regime from the federal government.Once scaled-up testing of both kinds becomes available (testing for infection and for immune response) some of our blue states may do the work to give us good numbers.
I think that historians will have to use demographic data and population changes to infer the actual COVID-19 death rate for many nations.
dmsilev
@Matt McIrvin:
Alternate theory: Californians are naturally genetically superior to the rest of the country.
Cheryl Rofer
@jl: I’ve thought of something like that for a followon post. It would require a fair bit conceptually and in research, so it’s not going to happen for a while, but it’s a reasonable question.
To boil it down to one line: We live with other communicable diseases for which we may not have full vaccine protection. Can that work for COVID-19?
jl
Another issue to consider, and something I didn’t see in the herd immunity tutorial is that any movement towards herd immunity does aid control efforts. Lack of herd immunity does not change the qualitative unstable versus stable equilibrium control problem. But getting closer to herd immunity does make the acute epidemic curve you have to endure while getting to the stable equilibrium slower and smaller.
So, OK, if NYC has 14 percent immunity, that can be used as a lever for design of reopening and planning outbreak control programs, gives more room for maneuver on testing programs. Risk of a large epidemic is smaller. And, the plausible range for ascertainment rate (proportion of infecteds that are currently identified) is huge. So, population surveys for prevalence of active past infection are very important guides to how to plan reopening and surveillance.
In next few weeks doesn’t mean much for NY or NJ, or Detroit or New Orleans, though. Maybe for CA, MN, OR, NM, makes a difference in terms of current planning.
Subsole
@Mary G: Even growing up around that attitude and soaking in the same fucking propaganda, it still floors me how utterly small and narrow and miserly and just mean -in every sense of the word- these people are.
cain
Yeah, but the people who want to shelter in place can’t do it unless they work for some kind of multi-state or international firm – otherwise everyone working in warehouses and the like will be required to go to work putting people in danger.
Meanwhile in the blue states, the Republicans and Trumpsters will be agitating to open things up and doing major FUD and campaigns to get the economy open.
Later, everyone will blame the Democratic party for not being adults. FIN.
Subsole
@Matt McIrvin: I am starting to wonder if Rush didn’t lie to get his shiny little medal.
jl
Also, a couple of questions, for Cheryl as an NM person. From data on testing I’ve seen, NM was very early and very aggressive, and so far has kept its epidemic much smaller and slower growing that in most places. But what was the add on to testing to make that happen? Did they have a contact tracking and quarantine program there?
And I’ve read there are some bad hotspots, particularly Native American populations. Is that true? Did NM drop the ball there?
patrick Il
@Cheryl Rofer:
If I understand your numbers correctly, I think the IFR would be more accurate if the denominator is the reported number of cases from a week or two ago, more or less.
Cheryl Rofer
@jl: Our governor has committed to testing for everybody. I haven’t followed it closely, but I think we’re something like third in the nation in per-capita testing. We also started social distancing measures early on.
The pueblos and the Navajo Nation are having a hard time. I don’t know the reasons for that and don’t want to speculate.
Cheryl Rofer
@patrick Il: I’m not calculating IFR, but rather estimating the fraction of immune people in the population.
The Moar You Know
This is a really dangerous assumption. By way of example, HIV produces massive amounts of antibodies, but those antibodies confer no immunity to the virus at all. Herpes simplex is another example. A slew of other viral bugs.
I’d like to see this proven before public health proceeds with it as a given. We all know what the odds of that are.
khead
I am very skeptical that there will even be any sporting events to go to before next year.
jl
@khead: Horsehoes? Might make a comeback.
Calouste
@lgerard: Navaro is yet another dimwit Harvard grad. I think we had one show up in the news every day this week.
Cheryl Rofer
@The Moar You Know: I am not advocating that this be the basis for public health policy. I am doing a rough estimate to evaluate claims for opening up the country
ETA: That is why I said, “For now.” And yes, I am aware that there is a range of antibody responses to viruses.
Calouste
@joel hanes:
All places with a woman as Prime Minister.
Brachiator
@Matt McIrvin:
So, the lockdown is a gigantic game of “let’s pretend?”
If California had immunity, we would have even fewer deaths and would all be out at the beach surfing.
This is insane. Limbaugh and Hanson know it is insane. But they get off on participating in the right wing grift.
The Thin Black Duke
@Calouste: Thank you for pointing this out. And I try not to think about how different things would be today if Hillary Clinton was President of the United States.
Fair Economist
@NYCMT:
Of course not. There are towns in Italy where > 0.5% of the *entire* population has already died. Most deaths aren’t officially attributed to COVID, but they wouldn’t be dead if it hadn’t happened. Most are likely patients who died of COVID at home because there was no room in the hospital, with a significant minority dying of other conditions, but we may never know.
debbie
At last, my mask arrived!
Baud
@The Thin Black Duke: Max 500 dead from Covid, leading to a Republican-led media-fueled campaign for her resignation or impeachment.
jl
@Brachiator: Well, even if the very lowest low end estimates of case ascertainment rate ( around 1 or 2 percent) that I find implausible, are correct, that hasn’t happened.
And, a consequence of CA being able to keep epidemic smaller, means, we have to plan for reopening and outbreak control more carefully, since a rebound acute epidemic will be nearly as dangerous as what we just went through. A problem I’m glad to have in CA, but a problem, nevertheless.
James E Powell
@Matt McIrvin:
The right wingers are willing to believe anything as long as it means they can hold onto their bigotries and continue worshiping their god-emperor.
khead
@jl:
I’m such a degenerate that I would probably bet on horseshoes right now… but Delaware Park is closed.
joel hanes
@The Moar You Know:
Herpes is a retrovirus. Completely different thing.
There are other coronaviruses in circulation among humans — one of them produces a variety of “the common cold”. We know how they behave, and people develop immunity.
By the way, how are your teeth? I’ve been worrying about you.
joel hanes
@khead:
I should have said “amateur sporting events” — e.g. softball games. The pros have professional management, and much money at risk, but I’m skeptical that even the trump of doom would prevent Texas boys from playing football in the fall.
Fair Economist
@Calouste:
Also Taiwan (with the best success to date of any country), Norway, Iceland, and Denmark. Damn.
dmsilev
@The Thin Black Duke: The Post had a depressingly plausible column about what that might be like:
How is the pandemic going on Earth 2 under President Hillary Clinton?
The Thin Black Duke
@Baud: Of course. Even in an alternative reality, some things never change.
Baud
@James E Powell:
A major reason Rush or Fox or Trump has so much credibility with the base is because they are the only ones who tell the “truth” about race.
debbie
@The Moar You Know:
My local NPR station ran a Q&A with an OSU pulmonologist about COVID-19 that ran almost an hour and was really informative. Among other things, he said not to expect immunity from COVID-19 to last more than a couple of months.
TriassicSands
Herd immunity?
That’s when Trump sends the “herd” back to work prematurely and he’s “immune” to accountability for the unnecessary deaths.
In the “Age of Trump” everything gets a new definition.
zzyzx
@debbie: if that’s true, how would vaccines work?
At that point, I think we shrug our shoulders and prepare for a lot of deaths :(
J R in WV
@debbie:
I’m not sure how he “knows” that… if true it means we are fucked as a civilization.
We will wind down into farmers and gardeners in remote places, rather than placing research facilities into orbit, toying with fusion power, trying to end global climate change, etc.
RobertC
In a randomly mixing homogeneous population, the herd immunity threshold is 1 – 1/R, so if R is 3, the herd threshold immunity is 1 – 1/3 = 66.7%.
Because our population isn’t quite randomly mixing homogenous, that’s a lower bound. The real world herd immunity threshold is a little higher than that.
So, bottom line: if we don’t find a vaccine, cases increase until we reach around 66.7% of the population infected. There are 330 million Americans, so that’s around 220M. That could be soon, that could be long and far away, but that’s how many need to have had the infection until herd immunity threshold is reached (once again, if there is no vaccine).
If the infection fatality rate were X% the deaths due to COVID-19 would be X% of 220M, so if X% were, say, 0.2%, that would mean 440,000 deaths.
So let’s hope we can keep R low through mitigation until a vaccine is developed.
BTW, R is independent of time so even if R > 1 it matters for the growth rate of infections (and thus deaths) if the time duration until a contagious person infects R others is short vs. long. So that’s another reason why social distancing matters — even if R is high you want the “generation length” to be long.
debbie
@zzyzx: @J R in WV:
It’s not like the flu shot provides longterm immunity either. Viruses are constantly adapting and changing.
joel hanes
@debbie:
The flu shot does not confer long-lasting immunity because influenza, a DNA virus, is a chameleon, and the genes for the proteins in its shell, to which the immunity is keyed, continually mutate. The immunity to the strain you’ve had remains, but the your immune system will not recognize the flu virus that arrives a year or two later, because the proteins are different — to your immune system, it looks like a different virus entirely.
SARS-CoV-2, like all coronaviruses, is an RNA virus. They tend to mutate more slowly. Scientists have been sequencing the RNA genome of the samples they receive — that’s how they know that the east coast was mostly infected from Europe — and the shell proteins have not so far been mutating in a way that would defeat acquired immunity.
Pehaps, once a vaccine steps on this coronavirus, the strains that persist will be ones that mutate the key proteins more quickly, but that’s just speculation at this point.
Brachiator
@dmsilev:
This is ridiculous. Everyone knows that in Earth 2, President Clinton worked with Wonder Woman and the Justice League to eliminate the pandemic before it even got started.
The Republicans still tried to impeach President Clinton again over her emails, and for working with foreign agents.
Sam
@joel hanes: I agree, with some caveats.
Trump doesn’t have the power he thinks he has. In the face of a life threatening virus, ordinary people have a vote. Governors have the most formal authority.
The rural areas and the proudly stupid never stopped being rural and stupid, so the differential impact of these categories “going back to work” will be relatively low.
The people that will be catastrophically impacted by poor policy are the poor and vulnerable, as always. I am looking forward to a time of pitchforks. Eventually all those exploited people will have had enough.
Sam
@joel hanes: I agree, with some caveats.
Trump doesn’t have the power he thinks he has. In the face of a life threatening virus, ordinary people have a vote. Governors have the most formal authority.
The rural areas and the proudly stupid never stopped being rural and stupid, so the differential impact of these categories “going back to work” will be relatively low.
The people that will be catastrophically impacted by poor policy are the poor and vulnerable, as always. I am looking forward to a time of pitchforks. Eventually all those exploited people will have had enough.
@jl: I don’t think this will play out by rational policy. There is no history that would suggest that rational policy is even feasible for this administration. We are to be victims of the whims of a very dumb narcissist.
Sam
Trump will reopen early, because what does he have to lose? If he doesn’t have the economy revved up in the fall, he loses. So he has to wish corona away soon. If the result is a lot of death, we’ll, he just loses by more. So it is a no-brainer for him. I really believe this is the way he thinks.
Dirk Reinecke
I think everybody is mistaken. We are Earth-2. The divergent problem filled time-line. The warning one. In other news, South Africa’s lockdown has been extended with another 14 days. This means that for the entire month of April South Africa will have been under one of the strictest lockdowns in the world. So far only 24 deaths and around 3000 infections.
Chris Johnson
@Matt McIrvin:
If they can get Californians to believe this shit, more Californians will die.
Pretty sure that’s the real purpose here. California is a blue state. If these people can get residents of blue states to ditch pandemic mitigation methods, they can get residents of blue states to die en masse, and thus outvote them.
…with the corpses of residents of red states? It’s still really stupid in spite of being really evil. But I’m sure they’re frantic to get the libs to abandon their isolation, and not just for ‘getting America back to work’. Some of these people understand what’s happening, and it guides their investments and public statements.
TheOtherHank
@zzyzx: One problem is that corona viruses (and influenza) use RNA for the their genomes rather than DNA. The DNA replication machinery in your cells has error checking and correction built in; RNA does not. The chances of a base (A, C, G, or T(or in RNA U)) added in being wrong in either DNA or RNA synthesis is fairly good (I mean it’s small, but over thousands/millions/billions of operations, the numbers mount up). In DNA this ususally gets fixed, but in RNA it doesn’t. So, RNA viruses evolve quickly, thus the proteins that vaccines are based on change quickly too. This is the main reason you need to get a new flu shot every year. The vaccine you got last year works on last year’s flu, but in the intervening time the proteins have changed just enough that a new vaccine is required to get you immunity this year. The common cold, as someone already stated, is also a corona virus and to a first approximation you never catch the same cold twice, but there are so many versions of the cold virus around that you keep catching a new one.
So it’s highly likely that any immunity from a covid 19 infection or a vaccination will work great on the particular strain it recognizes, but if the space of allowable coat protein sequences is large, then you’ll keep being presented with new versions of the virus that your immune system doesn’t recognize.
NYCMT
@Fair Economist: my sister (UMICH MPH ’04) works in corporate health policy in Frankfurt and has her own opinions are why German reported CFR is so low.
Meyerman
@joel hanes
All influenza viruses consist of single-stranded RNA as opposed to dual-stranded DNA.
https://www.cdc.gov/flu/about/professionals/genetic-characterization.htm
Coronaviruses possess the largest genomes (26.4 to 31.7 kb) among all known RNA viruses…
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3185738/
ziggy
We have many real-time experiments going on right now (Sweden, some of the states, Wuhan), and the results of these will give us a lot more information about how to proceed. If any of these fail miserably, we are going to see that and it will affect the choices people make, despite any decisions made by the White House. It seems pretty clear to me that at least the responsible states are not going to just “open up”. Life for us is not going to be the way it was for a long time. We may have restrictions on gatherings, take-out food, work from home if at all possible, restricted travel, even wearing a mask in public, until a vaccine is widely available.
Fair Economist
@joel hanes: Both influenza and coronaviruses are RNA viruses and rapidly mutating. Coronaviruses mutate more slowly because they have an error correcting polymerase which fixes about 2/3s of errors.
Influenza also has multiple “chromosomes” and can do “chromosome swaps” with another influenza infecting the same cell, creating a new virus with new antigenicity. This is rare but happens every few decades in a big way (e.g. 2009 swine flu) and probably more often in a small way. Coronaviruses can’t do this because they only have one chromosome. They can cross-repair to similar effect but it seems much rarer.
egorelick
@The Moar You Know: Most (all?) of the infections that produce antibodies that don’t confer immunity do not clear the disease. Also, antibodies are produced to different parts of the virus and in these cases, only one is usually important (like Hep B) except for case tracking purposes. We know that COVID-19 clears the body in some (most) people so this the assumption stated is pretty good.
bluefish
Thank you so much for this piece. Lucid and informative. Will read it again and again as I struggle to understand.
egorelick
Ok. Reading all the comments and there is a lot of conflation. Immunity (and here we are talking about antibody type immunity) has 3 elements:
1. Recognition – the foreign protein has to be recognized. Mutation defeats this.
2. Attack- the antibodies have to be able to attack the disease. Hiding in cells (and I believe other strategies) defeats this.
3. Memory – this is similar to the recognition problem but it is about whether the immune system retains a memory of the foreign protein. That memory resides in cells and not antibodies. Trying to remember a class long ago, but the cells that produce antibodies are different than the ones that have memory and (re)start the antibody producing function.
Vaccines need to be able to trigger recognition and memory. That’s why the shingles vaccine is given. You have the virus in you, but the body’s memory is weak of non-existent so its emergence needs to be recognized and attacked quickly to prevent painful outbreaks.
Cheryl Rofer
Please, please do not share “information” unless you can back it up.
SARS-CoV-2 is an unusually stable virus, with few mutations. Here’s one article on the subject. I have also been told this by a biochemist friend who is in the thick of things right now.
There are several assertions on this thread that because SARS-CoV-2 is an RNA virus, it has a high rate of mutation. WRONG. Please check information before you share it.
ballerat
@James E Powell:
This is exactly what I am seeing with some of my trumper family members.
I am convinced bigotry is a form of mental illness.
joel hanes
@Meyerman:
Thanks for the correction.
I should have googled.
I regret the error.
Bill Arnold
Re masks, a few new articles.
Face masks for the public during the covid-19 crisis (09 April 2020)
Physical interventions to interrupt or reduce the spread of respiratory viruses. Part 1 – Face masks, eye protection and person distancing: systematic review and meta-analysis (April 07, 2020)
And humor with a point (about the precautionary principle)
Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials. (2006)
(There are more like that one in the same genre.)
And here’s a list of countries that require or strongly recommend mask usage. Some only in the last week so their numbers won’t have changed yet if there is an effect.
Coronavirus: Countries where face masks are mandatory in COVID-19 fight (07 April 2020, Lana Andelane)
There are “natural experiments” being done. I strongly suspect that the WHO’s anti-mask recommendations will be found in future analyses to have been a serious error (resulting in many deaths) because masks block virus-containing droplet sprays from presymptomatic and asymptomatic individuals and reduce R0 significantly when combined with other measures. The church cluster in South Korea and the choir cluster in Washington and the Connecticut party cluster strongly suggest that superspreaders (and lesser asymptomatic spreaders) exist and that masking them by masking everyone would be a good idea.
otmar
Two interesting studies from Germany and Austria.
leeleeFL
@dmsilev: I thought someone would say that! Probably Rush.