Tag Archives: Transmissability

Chill-Out Advisory: Pandemic to Endemic Means Live Again

13 Sunday Feb 2022

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We might be just be done with the coronavirus pandemic. That is, it appears to be transitioning to a more permanent endemic phase. What follows are a few details about the Omicron wave and its current status, an attempt to put the risks of Covid in perspective, and a few public policy lessons that are now gaining broad currency but should have been obvious long ago.

What’s The Status?

The Omicron variant became the dominant U.S. strain of the coronavirus in December. Omicron outcompeted Delta, which was very good news because Omicron is far less severe. The chart below (from the CDC Data Tracker site) shows Omicron’s rapid ascendance and displacement of the Delta variant. The orange bar segments represent the proportion of cases of the Delta strain, while the purple and pink segments are Omicron sub-variants known as BA.1 and BA.2, respectively. BA.2 is even more transmissible than BA.1 and is likely to become dominant over the next month or so. However, the BA.2 sub-variant appears to be far less virulent than Delta, like BA.1.

Despite a record number of infections over a period of a month or so, the Omicron wave is tapering just as rapidly as it ramped up, as the next chart demonstrates. In fact, covidestim.org shows that cases are now receding in all states, DC, and Puerto Rico. Here are new cases per million people from Our World in Data:

Whether BA.2 causes cases to plateau for a while, or even a secondary Omicron “wavelet”, is yet to be seen. That would be consistent with the normal Hope-Simpson seasonal pattern of viral prevalence in the northern hemisphere (hat tip: HOLD2):

Data problems make the Omicron wave difficult to assess, however. We don’t know the share of incidental infections for the U.S. as a whole, but more than half of hospitalized Covid patients in Massachusetts and Rhode Island are classified with incidental infections. The proportion in the UK is estimated to be rising and approaching 30% of total cases, with much higher percentages in many regions of England, as shown below.

As I’ve emphasized in the past, case numbers should not be the primary gauge of the state of the pandemic, especially with a more highly contagious but relatively mild variant like Omicron. Hospitalizations are a better measure, but only if “incidental” infections are removed from the counts. That’s been acknowledged only recently by the public health establishment, and even the Biden Administration is emphasizing it as a matter of sheer political expediency. Another measure that might be more reliable for assessing the pandemic in the community as a whole is the number of emergency room patients presenting Covid-like symptoms. From the CDC Data Tracker:

There is no doubt that incidental infections create complications in caring for patients with other ailments. That has a bearing on the utilization of hospital capacity. Generally, however, strains on hospital capacity during the pandemic have been greatly exaggerated. This is not to diminish the hard work and risks faced by health care workers, and there have been spot shortages of capacity in certain localities. However, in general, staffed beds have been more than adequate to meet needs. This chart, like a few others below, is courtesy of Phil Kerpen:

With the more highly transmissible variants we have now, it’s not at all surprising to see a high proportion of incidental cases among inpatients. Incidental infections are likely to inflate counts of Covid deaths as well, given the exceptional and odd way in which Covid deaths are being recorded. It will be some time until we see full U.S. data on cases and deaths net of incidental infections. Moreover, many of the Covid deaths in December and January were from lingering Delta infections, which might still be a factor in the February counts.

How Are Your Odds?

The mild or asymptomatic nature of most Omicron cases, the large proportion of incidental hospitalizations, and the knowledge that Omicron is not a deep respiratory threat should offer strong reassurance to healthy individuals that the variant does not pose a great risk. According to a recent CDC report, in a sample of almost 700,000 vaccinated individuals aged 65 or less without co-morbidities, there were no Covid fatalities or ICU admissions during the 10 months from December 2020 through October 2021. There was only one fatality in the sample of healthy individuals older than 65. There were just 36 fatalities across the full sample of over 1.2 million vaccinated individuals, so COVID’s fatality risk was only about 0.3%. Of those deaths, 28 were among those with four or more risk factors (including co-morbidities and > 65 years). And this was before the advent of Omicron!

I have a few doubts about the CDC’s sample selection and vagaries around certain definitions used. Nevertheless, the results are striking. However, the study did not address risks to unvaccinated adults. Another more limited CDC study found that vaccinated patients were still less likely than the unvaccinated to require critical care during the Omicron wave.

A separate CDC study found a 91% reduction in the likelihood of death for Omicron relative to Delta. A study from the UK (see summary here) found that Omicron cases were 59% less likely than Delta cases to require hospitalization and 69% less likely to result in death within 28 days of a positive test. Omicron was far less deadly among both the vaccinated and the unvaccinated, and the latter had a larger reduction in the likelihood of death. The study was stratified by age as well, with less severe outcomes for Omicron among older cohorts except in the case of death, for which there was no apparent age gradient.

Another unnecessarily contentious issue has been the risk to children during the pandemic. Based on the data, there should never have been much doubt that these risks are quite low. Apparently, however, it was advantageous for teachers’ unions to insist otherwise. Phil Kerpen soundly debunks that claim with the following chart:

Covid has been less deadly to children from infancy through 17 years than the pre-pandemic flu going back to 2012! Oh yes, but teachers FEAR transmission from the children! That claim is just as silly, since children are known to be inefficient transmitters of the virus (and see here).

Now that Omicron has relegated the Delta variant to the history books, the risks going forward seem much more manageable. Omicron is less severe, especially for the vaccinated. Levels of acquired (natural) immunity from earlier infections are now much higher against older strains, and Omicron infections seem to be protective against Delta.

In commentary about the first CDC study discussed above, John Tierney lends perspective to the odds of death from pre-Omicron Covid:

“Those are roughly the same odds that in the course of a year you will die in a fire, or that you’ll perish by falling down stairs. Going anywhere near automobiles is a bigger risk: you’re three times more likely during a given year to be killed while riding in a car, and also three times more likely to be a pedestrian casualty. The 150,000-to-1 odds of a Covid death are even longer than the odds over your lifetime of dying in an earthquake or being killed by lightning.”

Yet with all this research confirming the low odds of death induced by Omicron, why have we seen recent deaths at levels approaching previous waves? First, many of those deaths are carried over from Delta infections. That means deaths should begin to taper rapidly as February reports roll in. And remember that daily reports do not show deaths by date of death. Deaths usually occur weeks or even months before they are reported. That also means some of the deaths reported might be “harvested” from much earlier fatalities. Second, given the high levels of incidental Omicron infections, some of those deaths are misattributed to Covid, an issue that is not new by any means. Finally, while Omicron is relatively mild for most people, the high rate of transmission means that a high number of especially vulnerable individuals may be infected with severe outcomes. We have seen much more severe consequences for the unvaccinated, of course, and for those with co-morbidities.

Things We Should Have Known

I’ll try to keep this last section brief, but as an introduction I’ll just say that it’s almost as if we’ve been allowing the lunatics to run the asylum. To paraphrase one comment I saw recently, if you wonder why there is so much dissent, you ought to consider the fact the much of what our governments have done (along with many private organizations) was to prohibit things that were demonstrably safe (e.g., going outside, using swing sets, or attending schools) and to encourage things that were demonstrably harmful (e.g., deferring medical care, or masking small children).

The following facts are only now coming into focus among those who’ve been “following the politics” rather than “the science”, despite pretensions to the latter.

Grow Up and Chill Out!

Life is full of risks, and nothing has changed to alter wisdom gained in earlier pandemics. For example, this pearl from a 2006 publication on disease mitigation measures should be heeded (hat tip: Phil Kerpen):

If there is one simple message everyone needs to hear, it is to stop allowing the virus bogeyman to rule your life. It will never go away completely, and it is likely to present risks that is are comparable to the flu going forward. In fact, it might well compete with the flu, which means we won’t be dealing with endemic Covid plus historical flu averages, but some smaller union of the two case loads.

So get out, go back to work, or go have some fun! Get back truckin’ on!

Vagaries of Vaccine Efficacy

23 Sunday Jan 2022

Posted by in Coronavirus, Vaccinations

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There should never have been any doubt that vaccines would not stop you from “catching” the coronavirus. Vaccines cannot stop virus particles from lodging in your nose or your eyeballs. The vaccines act to prime the immune system against the virus, but no immune response is instantaneous. In other words, if you aren’t first “infected”, antibodies don’t do anything! A virus may replicate for at least a brief time, and it is therefore possible for a vaccinated individual to carry the virus and even pass it along to others. The Omicron variant has proven that beyond a shadow of a doubt, though the wave appears to be peaking in most of the U.S. and has peaked already in a few states, mostly in the northeast.

I grant that the confusion over “catching” the virus stems from an imprecision in our way of speaking about contracting “bugs”. Usually we don’t say we “caught” one unless it actually makes us feel a bit off. We come into intimate contact with many more bugs than that. The effects are often so mild that we either don’t notice or brush it off without mention. But when it comes to pathogens like Covid and discussions of vaccine efficacy (VE), it’s obviously useful to remember the distinction between infections, on the one hand, and symptomatic infections on the other.

Cases Are the Wrong Focus

Unless calibrated by seroprevalence data, these studies are not based on proper estimates of infections in the population. Asymptomatic people are much less likely to get tested, and vaccinated individuals who are infected are either much more likely to be asymptomatic or the test might not detect the weak presence of a virus at all. VE based on detected infections is essentially meaningless unless testing is universal.

We are bombarded by studies (and analyses like the one here) alleging that VE should be judged on the reduction in infections among the vaccinated. The likelihood of a detected infection by vaccination status is simply the wrong way to measure of VE. It’s not so much the direction of bias in measured VE, however. The mere presence of cases among the vaccinated has been sufficient to inflame anti-vax sentiment, especially cases detected in mandatory tests at hospitals, where the infections are often incidental to the primary cause of admission.

The typical evolution of a novel virus is further reason to dismiss case numbers as a basis for measuring VE. Mutations create new variants in ways that usually promote the continuing survival of the lineage. Subsequent variants tend to be more transmissible and less deadly to their hosts. Thus, given a certain “true” degree of VE, so-called breakthrough infections among the vaccinated are even more likely to be asymptomatic and less likely to be tested and/or detected.

There is the matter of immune escape or evasion, however, which means that sometimes a virus mutates in ways that get around natural or vaccine-induced immune responses. While such a variant is likely to be less dangerous to unvaccinated hosts, more cases among the vaccinated will turn up. That should not be interpreted as a deterioration in VE, however, because detected infections are still the wrong measure. Instead, the fundamental meaning of VE is a lower virulence or severity of a variant in vaccinated individuals than in unvaccinated individuals.

Interestingly, to digress briefly, while immune escape has been discussed in connection with Omicron, that variant’s viral ancestors may have predated even the original Covid strain released from the Wuhan lab! It is a fascinating mystery.

Virulence

In fact, vaccines have reduced the virulence of Covid infections, and the evidence is overwhelming. See here for a CDC report. The chart below is Swiss data, followed by a “handy” report from Wisconsin:

From the standpoint of virulence, there are other kinds of misguided comparisons to watch out for: these involve vaxed and unvaxed patients with specific outcomes, like the left side of the graphic at the top of this post (credit to Twitter poster aparachick). This thread has an excellent discussion of the misconception inherent in the claim that vaccines haven’t reduced severity: the focus is on the wrong conditional probability (again, like the left side of the graphic). Getting that wrong can lead to highly inaccurate conclusions when the sizes of the two key groups, hospitalizations and vaccinated individuals in this case, are greatly different.

Bumbled Messaging

The misunderstandings about VE are just one of many terrible failures of public health authorities over the course of the pandemic. There seems to have been fundamental miscommunication by the vaccine manufacturers and many others in the epidemiological community about what vaccines can and cannot do.

Another example is the apparent effort to downplay the importance of natural immunity, which is far more protective than vaccines. This looks suspiciously like a willful effort to push the narrative that universal vaccination as the only valid course for ending the pandemic. Even worse, the omission was helpful to those attempting to justify the tyranny of vaccine mandates.

Waning Efficacy

It should be noted that the efficacy of vaccines will wane over time. This phenomenon has been measured by the presence of antibodies, which is a valid measure of one aspect of VE over time. However, immune responses are more deeply embedded in the human body: so-called T-cells carry messages alerting so-called B-cells to the presence of viral “invaders”. The B-cells then produce new antibodies specific to characteristics of the interloping pathogen. Thus, these cells can function as a kind of “memory” allowing the immune system to mount a fresh antibody defense to a repeat or similar infection. The reports on waning antibodies primarily in vaccinated but uninfected individuals do not and cannot account for this deeper process.

Conclusion

Vaccines don’t necessarily reduce the likelihood of infection or even the spread of the virus, but they absolutely limit virulence. That’s why Jay Bhattacharya, one of the authors of The Great Barrington Declaration, says the vaccines provide a private benefit, but only a limited public benefit. Yet too often we see VE measured by the number of infections detected, and vaccine mandates are still motivated in part by the idea that vaccines offer protection to others. They might do that only to the extent that infections are less severe and clear-up more quickly.

Vax Results, Biden Boosters, Delta, and the Mask Charade

19 Thursday Aug 2021

Posted by in Coronavirus, Public Health, Uncategorized, Vaccinations

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If this post has an overarching theme, it might be “just relax”! That goes especially for those inclined to prescribe behavioral rules for others. People can assess risks for themselves, though it helps when empirical information is presented without bias. With that brief diatribe, here are a few follow-ups on COVID vaccines, the Delta wave, and the ongoing “mask charade”.

Israeli Vax Protection

Here is Jeffrey Morris’ very good exposition as to why the Israeli reports of COVID vaccine inefficacy are false. First, he shows the kind of raw data we’ve been hearing about for weeks: almost 60% of the country’s severe cases are in vaccinated individuals. This is the origin of the claim that the vaccines don’t work. 

Next, Morris notes that 80% of the Israeli population 12 years and older are vaccinated (predominantly if not exclusively with the Pfizer vaccine). This causes a distortion that can be controlled by normalizing the case counts relative to the total populations of the vaccinated and unvaccinated subgroups. Doing so shows that the unvaccinated are 3.1 times more likely to have contracted a severe case than the vaccinated. Said a different way, this shows that the vaccines are 67.5% effective in preventing severe disease. But that’s not the full story!

Morris goes on to show case rates in different age strata. For those older than 50 (over 90% of whom are vaccinated and who have more co-morbidities), there are 23.6 times more severe cases among the unvaccinated than the vaccinated. That yields an efficacy rate of 85.2%. Vaccine efficacy is even better in the younger age group: 91.8%. 

These statistics pertain to the Delta variant. However, it’s true they are lower than the 95% efficacy rate achieved in the Pfizer trials. Is Pfizer’s efficacy beginning to fade? That’s possible, but this is just one set of results and declining efficacy has not been proven. Israel’s vaccination program got off to a fast start, so the vaccinated population has had more time for efficacy to decay than in most countries. And as I discussed in an earlier post, there are reasons to think that the vaccines are still highly protective after a minimum of seven months.

Biden Boosters

IIn the meantime, the Biden Administration has recommended that booster shots be delivered eight months after original vaccinations. There is empirical evidence that boosters of similar mRNA vaccine (Pfizer and Moderna) might not be a sound approach, both due to side effects and because additional doses might reduce the “breadth” of the antibody response. We’ll soon know whether the first two jabs are effective after eight months, and my bet is that will be the case.

Is Delta Cresting?

Meanwhile, the course of this summer’s Delta wave appears to be turning a corner. The surge in cases has a seasonal component, mimicking the summer 2020 wave as well as the typical Hope-Simpson pattern, in which large viral waves peak in mid-winter but more muted waves occur in low- to mid-latitudes during the summer months.

Therefore, we might expect to see a late-summer decline in new cases. There are now 21 states with COVID estimated reproduction rates less than one (this might change by the time you see the charts at the link). In other words, each new infected person transmits to an average of less than one other person, which shows that case growth may be near or beyond a peak. Another 16 states have reproduction rates approaching or very close to one. This is promising.

Maskholes

Finally, I’m frustrated as a resident of a county where certain government officials are bound and determined to impose a mask mandate, though they have been slowed by a court challenge. The “science” does NOT support such a measure: masks have not been shown to mitigate the spread of the virus, and they cannot stop penetration of aerosols in either direction. This recent article in City Journal by Jeffrey H. Anderson is perhaps the most thorough treatment I’ve seen on the effectiveness of masks. Anderson makes this remark about the scientific case made by mask proponents:

“Mask supporters often claim that we have no choice but to rely on observational studies instead of RCTs [randomized control trials], because RCTs cannot tell us whether masks work or not. But what they really mean is that they don’t like what the RCTs show.”

Oh, how well I remember the “follow-the-science” crowd insisting last year that only RCTs could be trusted when it came to evaluating certain COVID treatments. In any case, the observational studies on masks are quite mixed and by no means offer unequivocal support for masking. 

A further consideration is that masks can act to convert droplets to aerosols, which are highly efficient vehicles of transmission. The mask debate is even more absurd when it comes to school children, who are at almost zero risk of severe COVID infection (also see here), and for whom masks are highly prone to cause developmental complications.

Closing Thoughts

The vaccines are still effective. Data purporting to show otherwise fails to account for the most obvious of confounding influences: vaccination rates and age effects. In fact, the Biden Administration has made a rather arbitrary decision about the durability of vaccine effects by recommending booster shots after eight months. The highly transmissible Delta variant has struck quickly but the wave now shows signs of cresting, though that is no guarantee for the fall and winter season. However, Delta cases have been much less severe on average than earlier variants. Masks did nothing to protect us from those waves, and they won’t protect us now. I, for one, won’t wear one if I can avoid it.

Herd Immunity To Public Health Bullshitters and To COVID

16 Monday Aug 2021

Posted by in Coronavirus, Herd Immunity, Uncategorized

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My last post had a simple message about the meaning of immunity: you won’t get very sick or die from an infection to which you are immune, including COVID-19. Like any other airborne virus, that does NOT mean you won’t get it lodged in your eyeballs, sinuses, throat, or lungs. If you do, you are likely to test positive, though your immunity means the “case” is likely to be inconsequential.

As noted in that last post, we’ve seen increasing COVID case counts with the so-called Delta variant, which is more highly transmissible than earlier variants. (This has been abetted by an uncontrolled southern border as well.) However, as we’d expect with a higher level of immunity in the population, the average severity of these cases is low relative to last year’s COVID waves. But then I saw this article in ScienceAlert quoting Sir Andrew Pollard, a scientist affiliated AstraZeneca and the University of Oxford. He says with Delta, herd immunity “is not a possibility” — everyone will get it.

Maybe everyone will, but that doesn’t mean everyone will get sick. His statement raises an obvious question about the meaning of herd immunity. If our working definition of the term is that the virus simply disappears, then Pollard is correct: we know that COVID is endemic. But the only virus that we’ve ever completely eradicated is polio. Would Pollard say we’ve failed to achieve herd immunity against all other viruses? I doubt it. Endemicity and herd immunity are not mutually exclusive. The key to herd immunity is whether a virus does or does not remain a threat to the health of the population generally.

Active COVID infections will be relatively short-lived in individuals with “immunity”. Moreover, viral loads tend to be lower in immune individuals who happen to get infected. Therefore, the “infected immune” have less time and less virus with which to infect others. That creates resistance to further contagion and contributes to what we know as herd immunity. While immune individuals can “catch” the virus, they won’t get sick. Likewise, a large proportion of the herd can be immune and still catch the virus without getting sick. That is herd immunity.

One open and controversial question is whether uninfected individuals will require frequent revaccination to maintain their immunity. A further qualification has to do with asymptomatic breakthrough infections. Those individuals won’t see any reason to quarantine, and they may unwittingly transmit the virus.

I also acknowledge that the concept of herd immunity is often discussed strictly in terms of transmission, or rather its failure. The more contagious a new virus, like the Delta variant, the more difficult it is to achieve herd immunity. Models predicting low herd immunity thresholds due to heterogeneity in the population are predicated on a given level of transmissibility. Those thresholds would be correspondingly higher given greater transmissibility.

A prominent scientist quoted in this article is Paul Hunter of the University of East Anglia. After backing-up Pollard’s dubious take on herd immunity, Hunter drops this bit of real wisdom:

“We need to move away from reporting infections to actually reporting the number of people who are ill. Otherwise we are going to be frightening ourselves with very high numbers that don’t translate into disease burden.”

Here, here! Ultimately, immunity has to do with the ability of our immune systems to fight infections. Vaccinations, acquired immunity from infections, and pre-existing immunity all reduce the severity of later infections. They are associated with reductions in transmission, but those immune responses are more basic to herd immunity than transmissability alone. Herd immunity does not mean that severe cases will never occur. In fact, more muted seasonal waves will come and go, inflicting illness on a limited number of vulnerables, but most people can live their lives normally while viral reproduction is contained. Herd immunity!

Sadly, we’re getting accustomed to hearing misstatements and bad information from public health officials on everything from mask mandates, lockdowns, and school closings to hospital capacity and vaccine hesitancy. Dr. Pollard’s latest musing is not unique in that respect. It’s almost as if these “experts” have become victims of their own flawed risk assessments insofar as their waning appeal to “the herd” is concerned. Professor Hunter’s follow-up is refreshing, however. Public health agencies should quit reporting case counts and instead report only patients who present serious symptoms, COVID ER visits, or hospitalizations.

COVID Cases Decline Despite New Variants

19 Friday Feb 2021

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For weeks, even months, we’ve been hearing about dangerous new mutations of the coronavirus, and they’ve been identified in cases in the U.S. There’s a UK strain, a South African strain, a Brazilian strain, and still others, which differ in seemingly minor ways. Nevertheless, these variants are said to be more infectious. It’s also been reported that the South African and Brazilian strains might resist antibodies from prior infections from earlier strains.

Kyle Lamb has provided the following charts to put things in perspective:

Just to round things out, here is the trend in cases worldwide:

There is a great deal of concern about the new variants. A search for “COVID-19 variants” turns up plenty of scary articles. However, there is some evidence that the new variants are not as dangerous as alarmists contend. The resistance to specific antibodies does not necessarily imply resistance to protection by T-cells. As Youyang Gu points out, even if a new strain becomes “dominant”, that does not imply that cases will reverse their decline. This study indicates that the Pfizer vaccine is protective against both the UK and South African strains, and there is evidence that other vaccines offer adequate protection as well (and see here).

The charts demonstrate that the new strains haven’t arrested or reversed the declines in infections witnessed worldwide since early January. That doesn’t mean the mutations haven’t made a difference: perhaps the declines would have been faster in their absence. And we don’t know what the future will hold as the virus in various forms becomes endemic. Still, it’s reassuring to see that the increased transmissibility of the new strains hasn’t overcome factors that have contributed to the recent declines, which in all likelihood are related to increasing immunity in the population with a minor assist from vaccinations (thus far). As Lamb wryly notes about the recent declines in transmission: “Just saying”.

Spate of Research Shows COVID Lockdowns Fail

27 Sunday Dec 2020

Posted by in Lockdowns, Public Health

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For clarity, start with this charming interpretive one-act on public health policy in 2020. You might find it a little sardonic, but that’s the point. It was one of the more entertaining tweets of the day, from @boriquagato.

A growing body of research shows that stringent non-pharmaceutical interventions (NPIs) — “lockdowns” is an often-used shorthand — are not effective in stemming the transmission and spread of COVID-19. A compendium of articles and preprints on the topic was just published by the American Institute for Economic Research (AEIR): “Lockdowns Do Not Control the Coronavirus: The Evidence”. The list was compiled originally by Ivor Cummins, and he has added a few more articles and other relevant materials to the list. The links span research on lockdowns across the globe. It covers transmission, mortality, and other health outcomes, as well as the economic effects of lockdowns. AIER states the following:

“Perhaps this is a shocking revelation, given that universal social and economic controls are becoming the new orthodoxy. In a saner world, the burden of proof really should belong to the lockdowners, since it is they who overthrew 100 years of public-health wisdom and replaced it with an untested, top-down imposition on freedom and human rights. They never accepted that burden. They took it as axiomatic that a virus could be intimidated and frightened by credentials, edicts, speeches, and masked gendarmes.

The pro-lockdown evidence is shockingly thin, and based largely on comparing real-world outcomes against dire computer-generated forecasts derived from empirically untested models, and then merely positing that stringencies and “nonpharmaceutical interventions” account for the difference between the fictionalized vs. the real outcome. The anti-lockdown studies, on the other hand, are evidence-based, robust, and thorough, grappling with the data we have (with all its flaws) and looking at the results in light of controls on the population.”

We are constantly told that public intervention constitutes “leadership”, as if our well being depends upon behavioral control by the state. Unfortunately, it’s all too typical of research on phenomena deemed ripe for intervention that computer models are employed to “prove” the case. A common practice is to calibrate such models so that the outputs mimic certain historical outcomes. Unfortunately, a wide range of model specifications can be compatible with an historical record. This practice is also a far cry from empirically testing well-defined hypotheses against alternatives. And it is a practice that usually does poorly when the model is tested outside the period to which it is calibrated. Yet that is the kind of evidence that proponents of intervention are fond of using to support their policy prescriptions.

In this case, it’s even worse, with some of the alleged positive effects of NPI’s wholly made-up, with no empirical support whatsoever! So-called public health experts have misled themselves, and the public, with this kind of fake evidence, when they aren’t too busy talking out of both sides of their mouths.

COVID Immunity, Herd By Herd

01 Tuesday Sep 2020

Posted by in Coronavirus, Herd Immunity

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Too many public health authorities remain in denial, but epidemiologists are increasingly convinced that heterogeneity implies a coronavirus herd immunity threshold (HIT) that is greatly reduced from traditional models and estimates. HIT is the share of the population that must be infected before the contagion begins to recede (and the transmission ratio R falls below one). Traditional models, based on three classes of individuals (Susceptibles, Infectives, and Recovered – SIR), predict a HIT of 60% or more. However, models that incorporate variation in susceptibility, transmissibility, and occupational or social behavior reduce the HIT substantially. Many of these more nuanced models show that the HIT could be in a range of just 15% to 25%. If that is the case, many regions are already there!

For background, I refer you to the first post I wrote about heterogeneity in late March, more detailed thoughts from early May, examples and more information on the literature later in May. I’ve referenced it repeatedly in other posts since then. And now, more than five months later, even the slow kids at the New York Times have noticed. The gist of it: if not everyone is equally susceptible, for example, a smaller share of the population needs to be “immunized via infection” to taper the spread of the virus.

Some supporting evidence appears in the charts below, courtesy of Kyle Lamb on Twitter. The first chart shows a seven-day average of C19 cases per million of population for ten states that reached an estimated 10% antibodies. These antibodies confer at least short-term immunity against C19. Most of these states saw cases/m climb at least through the day when the 10% level was reached, though Rhode Island appears to have been an exception.

The second chart shows the seven-day average of cases/m in the same states starting seven days after the 10% immunity level was reached. I’d prefer to see the days in the interim as well, but the changes in trend are still noteworthy. All of these states except Louisiana had a downturn in the seven-day average of new cases within a few weeks of breaching the 10% infection level (Louisiana had distinct and non-coincident outbreaks in different parts of the state). These striking similarities suggest that things turned as the infection level reached 15% or more, consistent with many of the epidemiological models incorporating heterogeneity.

Next, take a look at the states in which C19 surged most severely this summer. The new cases are not moving averages, so the charts are not quite comparable to those above. However, the peaks seem to occur prior to the breach of the 15% infection level.

Speculation about early herd immunity has been going on for several months with respect to various countries and even more “micro” settings such as cruise ships and military vessels, where populations are completely isolated. Early on, this “early” herd immunity was discussed under the aegis of “immunological dark matter”, but we know now that T-cell immunity has played an important role. In any case, anti-body expression (or seroprevalence) at around 20% has been linked to reversals in C19 cases and deaths in several countries. As Yinon Weiss notes, New York City and Stockholm were both C19 hotspots in the spring, both have seen deaths decline to low levels, and they have little in common in terms of public health policy. London as well. The one thing they share are similar levels of seroprevalence.

An important qualification is that herd immunity is not relevant at high levels of aggregation. That is, herd immunity won’t be achieved simultaneously in all regions. The New York City metro area might have reached its HIT in April, but Florida (or perhaps only Miami) might have reached a HIT in July. Many areas of the Midwest probably still aren’t there.

In the absence of a new mutation of C19, the final proof of herd immunity in many of the former hotspots will be in the fall and winter. We should expect at least a few cases in those areas, but if there are more intense contagions, they should be confined to areas that have not yet seen a level of seroprevalence near 15%.

Some Cheery COVID Research Tidbits

16 Thursday Jul 2020

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Here’s a short list of new or newish research developments, some related to the quest to find COVID treatments. Most of it is good news; some of it is very exciting!

Long-lasting T-cell immunity: this paper in Nature shows that prior exposure to coronaviruses like severe acute respiratory syndrome (SARS) and even the common cold prompt an immune reaction via so-called T-cells that have long memories and are reactive to certain proteins in COVID-19 (SARS-CoV-2). The T-cells were detected in both C19-infected and uninfected patients. This comes after discouraging reports that anti-body responses to C19 are short-lived, but T-cells are a different form of acquired immunity. Derek Lowe says the following:

“This makes one think, as many have been wondering, that T-cell driven immunity is perhaps the way to reconcile the apparent paradox between (1) antibody responses that seem to be dropping week by week in convalescent patients but (2) few (if any) reliable reports of actual re-infection. That would be good news indeed.”

The herd immunity threshold (HIT) is much lower than you think: I’ve written about the effect of heterogeneity on the HIT before, here and here. This new paper, by three Oxford zoologists, shows that the existence of a cohort having some form of prior immunity, innate or acquired, reduces the number of infections required to achieve the HIT. For example, if initial transmissibility (R0) is 2.5 and 40% of the population has prior immunity (both reasonable assumptions for many areas), the HIT is as low as 20%, according to the authors’ calculations. That’s when the contagion begins to recede, though the final infected share of the population would be higher. This might explain why new cases and deaths have already plunged in places like Italy, Sweden, and New York, and why protests in NYC did not lead to a new wave of infections, while those in the south appear to have done so.

Seasonal effects: viral loads might be decreasing. From the abstract:

“Severity of COVID-19 in Europe decreased significantly between March and May and the seasonality of COVID-19 is the most likely explanation. Mucosal barrier and mucociliary clearance can significantly decrease viral load and disease progression, and their inactivation by low relative humidity of indoor air might significantly contribute to severity of the disease.”

The BCG vaccine appears to be protective: this is the bacillus Calmette-Guérin tuberculosis vaccine administered in some countries, This finding is not based on clinical trials, so more work is needed.

Is there no margin in plasma? No subsidy? This is the only “bad news” item on my list. It’s widely agreed that blood plasma from recovered C19 patients can be incorporated into an immune globulin drug to inoculate people against the virus. It’s proven safe, but for various reasons no one seems interested. Not the government. Not private companies. Did Trump happen to mention it or something?

C19 doesn’t spread in schools: this German study demonstrates that there is little risk in reopening schools. One of the researchers says:

“Children act more as a brake on infection. Not every infection that reaches them is passed on…. This means that the degree of immunization in the group of study participants is well below 1 per cent and much lower then we expected. This suggests schools have not developed into hotspots.”

Also worth emphasis is that remote learning leaves much to be desired, as acknowledged by the National Academies of Science, Engineering and Medicine, which has recommended that schools reopen for younger children and those with special needs.

Can angiotensin drugs (ACE Inhibitors/ARBs) reduce mortality? This meta-analysis of nine studies finds that these drugs reduce C19 mortality among patients with hypertension. The drugs were also associated with a reduction in severity but not with statistical significance. These results run contrary to initial suspicions, because ACEI/ARB drugs actually “up-regulate” ACE-2 receptors, to which C19 binds. Researchers say the drugs might be working through some other protective channel. This is not a treatment per se, but this should be reassuring if you already take one of these medications.

Tricor appears to clear lung tissue of C19: this research focused on C19’s preference for an environment rich in cholesterol and other fatty acids:

“What they found is that the novel coronavirus prevents the routine burning of carbohydrates, which results in large amounts of fat accumulating inside lung cells – a condition the virus needs to reproduce.”

Tricor reduces those fats, and the researchers claim it is capable of clearing lung tissue of C19 in a matter of days. This was not a clinical trial, however, so more work is needed. Tricor is an FDA approved drug, so it is safe and could be administered “off label” immediately. Tricor is a fibrate; the news with respect to statins and C19 severity is pretty good too! These are not treatments per se, but this should be reassuring if you already take one of these medications.

Hydroxychloroquine works: despite months of carping from media and leftist know-it-all’s dismissing the mere possibility of HCQ as a potential C19 treatment, evidence is accumulating that it is effective in treating early-stage infections after all. The large study conducted by the Henry Ford Health System found that treatment with HCQ early after hospitalization, and with careful monitoring of heart function, cut the death rate in half relative to a control group. Here’s another: an Indian study found that four-plus maintenance doses of HCQ acted as a prophylactic against C19 infection among health care workers, reducing the odds of infection by more than half. An additional piece of evidence is provided by this analysis of a 14-day Swiss ban on the use of HCQ in late May and early June. The ban was associated with a huge leap in the C19 deaths after a lag of less than two weeks. Resumption of HCQ treatment brought C19 deaths down sharply after a similar lag.

Meanwhile, a study in Lancet purporting to show that HCQ was ineffective and posed significant risks to heart health was retracted based on the poor quality of the data.

Remdesivir also cuts death rate: by 62% in a smaller controlled study by the drug maker Gilead Sciences.

Pet ownership might confer some immunity: this one is a little off-beat, and perhaps the research is under-developed, but it is interesting nonetheless!

I owe Instapundit and Marginal Revolution hat tips for several of these items.