Archive for the ‘CDC’ Category

Walenshy on rapid tests … then and now.

January 18, 2022

Last week, we spotlighted a NY Times article “The C.D.C. Is Hoping You’ll Figure Covid Out on Your Own”.

Author Zeynep Tufekci asked:

Why, two years into the pandemic, are people are grasping to know whether they should see a grandparent or an elderly relative or go back to work if they are still testing positive?

Why are we still trying to figure this out on our own?

Of course, the primary root causes are a new, fast-moving, ever-changing virus … and haphazard science, heavily politicized, that can’t seem to converge on a coherent “theory of the case”.

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Now that Biden’s test kit program is about to launch, this part of the article has specific relevance….

Deep in the article, Tufekci  channels CDC Director Walensky to provide a clear explanation of covid testing … and an example of the politicization.

According to Tufekci…

Back in 2020, when Walensky was on the faculty of the Harvard Medical School and chief of the division of infectious diseases at Massachusetts General Hospital, she co-authored a scientific paper titled “Saliva-Based Antigen Testing Is Better Than PCR Swabs”.

Some snippets from that paper:

> PCR tests can detect tiny amounts of the virus, so they do a great job of “diagnostic testing” — determining early-on if you are infected and may require isolation or treatment.

> But, PCR tests can “return positives for as many as 6-12 weeks … long after a person has ceased to need medical care or pose any real risk of transmission to others.”

> Said bluntly: PCR tests do a good job of diagnostic testing but a rotten job of “surveillance testing” that zooms in on whether a person is contagious to others.

> “The antigen tests are ideally suited for surveillance testing since they yield positive results precisely when the infected individual is maximally infectious.”

The reason is that antigen tests respond to the viral load in the sample without biologically amplifying the amount of the virus. PCR tests do amplify the virus in the samples and sometimes detect and report inconsequential “left over” viral fragments.

> A rapid test turns positive if a sample contains high levels of the virus, not nonviable bits or minute amounts — and it’s high viral loads that correlate to higher infectiousness.

With respect to viral transmission: “False negatives” on rapid tests are a benefit since “those are true negatives for disease transmission”

Again, a PCR test is positive if any amplified viral content is detected.

An antigen test may be negative if the virus is present but the viral load is very low … consistent with a low likelihood of viral transmission.

> But, antigen tests may be slower (than PCR tests) to detect the early onset of an infection, especially if symptoms haven’t materialized, since the viral load may be low but building.

> So, confirming a suspected early stage infection is best done with a PCR test or with a series of rapid tests, say, every other day for a week.

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OK, that’s what Walensky said back in fall of 2020, before her shift from “scientist” to “political scientist”.

Now, she’s saying:

“We actually don’t know how our rapid tests perform and how well they predict whether you’re transmissible during the end of disease”

Has the science changed … or, the scientist?

Hmm

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P.S. Walensky’s entire 2020 paper is worth reading.

WaPo: “Flying blind is no way to survive a pandemic”

January 12, 2022

Finally, I agree with a Washington Post editorial.

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Amid the omicron spike, the recent uproar about testing and quarantine rules has spotlighted the current unscientific nature of “the science”.

Biden’s scientific team offers up simultaneously contradictory points of view, small scale ad hoc studies that incite reactionary course reversals, and no logical, fact-based “theory of the case”.

In the words of Rajiv J. Shah, president of the Rockefeller Foundation:

“The United States has been flying virally blind.”

More specifically, Shah argues:

Data is the secret weapon that has helped beat every disease outbreak over the last century.

Data is what moves us from a panic-driven response to a science-driven one, telling us how to fight back and which tools are best.

But, as Covid-19 swept the world one year ago, the United States under-prioritized the need for data and the tests that produce it.

The data-deficient response to Covid-19 is why this pandemic’s been so deadly, so disruptive and so costly.

Currently, only a handful of countries (e.g. Israel, South Africa, Britain) are systematically collecting, analyzing and sharing data that is sufficiently comprehensive, precise and timely to help public health authorities and scientists make informed decisions about relaxing precautions or adapting vaccines and treatments.

Unfortunately, from a data perspective, the United States is in no better position to understand and stop a viral variant today than it was before the pandemic started.

The United States has not yet built a real-time system of viral surveillance that would allow comprehensive tracking of variants as they move through the population.

As it is now, the CDC pulls together viral surveillance data from a variety of sources, including its own facilities, state public health labs, and university and private laboratories.

The frustrating complexity and diversity of electronic medical records is an ongoing challenge.

The data sets are minimally standardized, key data is often uncollected, data file formats vary and data reporting is sporadic.

So, it can take weeks to build a complete and reliable picture of how a variant is spreading.

By then, it’s often too late and a newer variant must be battled.

The U.S. must take crucial steps to support a national viral surveillance network to defeat Covid-19 and prepare for the next pandemic.

Bottom line: It’s not surprising that there’s no over-riding theory-of-the-case, confusion re: pivotal factors (e.g. prevalence, transmission, re-infection, mitigation effectiveness) and a seemingly endless pandemic.

Why is the CDC so reactionary, illogical and, uh, unscientific?

January 3, 2022

Their most recent isolation “guidance” is a case in point.
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With covid-omicron spreading like wildfire and seeming to close in on all of us (me included) … and with workforces getting depleted by quarantined workers, the CDC stepped in to save the day by issuing revised isolation guidelines, specifically:

Given what we currently know about COVID-19 and the Omicron variant, CDC is shortening the recommended time for isolation for the public.

People with COVID-19 should isolate for 5 days and if they are asymptomatic or their symptoms are resolving (without fever for 24 hours), then…

People should follow that (isolation period) by 5 days of wearing a mask when around others to minimize the risk of infecting people they encounter. CDC

Let’s unpack that guidance…

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First, when does the clock start running?

For somebody who who develops symptoms, I guess it’s when “the” symptoms first present themselves.

My questions:

(1) Do cold-like sniffles count as “symptoms”? What’s the best indicator that I may have caught it? How indicative is a fever?

(2) What to do if I am officially symptomatic? Isolate, for sure … but, go see a doctor?

Note: At local walk-in clinics, people are waiting 4 to 6 hours in a room filled with 50 to 100 sick-likely people.  Sounds like a recipe for disaster, right?

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What about infectees who are asymptomatic?

For them, I guess that the clock starts for when they test positive.

Let’s pretend that they’re inclined to get tested (say, because other members of their household are symptomatic or have tested positive … or because their employer or airline requires a test).

These folks can’t do-it-themselves now because of the scarcity of in-home rapid tests.

Of course, they have the option of waiting in line for a couple of hours to get a “commercial” PCR test.

Note: Lines are running around the block at local testing sites.  Again, sounds like a recipe for disaster since most of the people in line are symptomatic.

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Once the clock starts…

OK, this part of the CDC guidance is pretty clear: isolate for 5 days.

But, things get murky after that isolation period.

The CDC says:

After infectees isolate for 5 days, if they are asymptomatic or their symptoms are resolving (e.g. no fever for 24 hours), then…

They should follow that (isolation period) by 5 days of wearing a mask when around others

The criteria “asymptomatic or symptoms resolving” is most problematic.

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What about rapid tests?

In the UK and several other countries, that free-of-isolation criteria is supplemented by the need for a negative covid test … rapid tests qualify.

So, why isn’t the CDC advising a negative covid test?

Cynics observe that the omission of negative tests in the guidance is simply cover for the Biden Administration’s slow-roll on the development and production of antigen rapid tests.

The official CDC announcement says:

The guidance is motivated by science demonstrating that the majority of transmission occurs early in the course of illness, generally in the 1-2 days prior to onset of symptoms and the 2-3 days after infection. CDC

More specifically, CDC Director Rochelle Walensky told CNN that the CDC chose five days because that’s typically the period when individuals are most infectious.

“Those five days account for somewhere between 85 to 90 percent of all transmission that occurs”

So far,so good.

But then she added:

“We opted not to advise the rapid test for isolation because we actually don’t know how our rapid tests perform and how well they predict whether you’re transmissible during the end of disease. Source

Say, what?

So, if I have this right…

Biden has ordered up 500 million in-home rapid tests … but the CDC doesn’t “actually know how well rapid tests perform and how well they predict transmissible presence of the virus”.

If that isn’t dizziness-inducing enough, Dr. Fauci, Biden’s chief political scientist, was his usual ubiquitous self on Sunday TV hinting that the CDC would soon be adding a testing requirement after all. Source

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My take: It would be a lot easier to “follow the science” if “the science” weren’t so reactionary, illogical, impractical and, well, unscientific.

CDC guidance for vaccinated people…

March 9, 2021

Good news, common-sensical, scientifically-based … and, of course, politically-motivated.
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Yesterday, all media headlined CDC guidance for the steadily increasing pool of vaccinated Americans.

The political motivation: High risk seniors who are frustrated re: vaccine access and scheduling processes are asking: “Why go through the hassle of getting vaccinated if I still won’t be able to see my grandkids?”.

That vax-hesitancy is not good if the goal is to cut the Covid death rate and reach herd immunity.

Cutting to the chase: Based on the new CDC guidance, grandparents can now — without masks or socially distancing —  visit their grandchildren.

Of course, there’s plenty of fine print in the CDC guidance.

So. here’s what you need to know….

(more…)


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