Archive for the ‘COVID – Immunity’ Category

Covid data: More about breakthrough infections and viral transmission…

October 8, 2021

As we posted yesterday ……

In its recent application to get an Emergency Use Authorization for booster shots, Pfizer submitted data indicating that effectiveness against infection starts high (90% immediately after the 2nd shot) …  but it wanes down to around 40% 6 months later.

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From this data, we can infer some things about viral transmission … since infection is an obvious prerequisite to transmission.

Early on, soon after people get vaccinated, the risk of infection is very low, so the risk of transmission is very low.

But, as the vaccine’s protection from infection wanes, the transmission risk (among vaccinated people) increases.

The impact is, shall we say, statistically significant.

How significant?

Let’s run some numbers…

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How many transmitters?

In rough numbers that are good enough to calibrate the transmission impact, about 200 million people have been vaccinated and about 100 million haven’t been.

Using those ballpark numbers to determine the magnitude of effect …

In the spring, shortly after the first rush-to-get-vaccinated, there were about 100 million unvaccinated people who were vulnerable to infection and, thus, transmission.

At the same tome, 10% (the inverse of 90%) of the vaccinated people, about 20 million, were vulnerable to infection and transmission.

So, the total number of people vulnerable to infection and transmission was 120 million.

But, 6 months later, as the vaccinations aged & waned, 60% of the vaccinated people, about 120 million were vulnerable to infection and transmission.

So, the total number of people vulnerable to infection and transmission was 220 million … over half of whom were fully vaccinated.

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So what?

Everybody knows that cases started spiking this summer.

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The culprits behind the spike: the Delta variant … and unvaccinated people.

Or, so we’ve been told,

Delta is guilty as charged, but …

Because of the aging of Spring vaccination shots … and the associated waning of infection protection … our rough-cut estimate is that, pre-booster shots, more than half of the people spreading the virus are probably vaccinated people whose infection protection has waned.

They’re unindicted (and unnamed) co-conspirators behind the spike in cases.

In stats-speak: Bayes is alive and well … but oft-overlooked.

More: About infection and transmission…

October 7, 2021

Earlier this week we posted

1. The CDC web site says that it is very rare for a vaccinated person to get infected and transmit the virus.

2. Fauci opined a similar view in a CNBC interview … but equivocated when confronted with some compelling anecdotal evidence and couldn’t brandish CDC data to the contrary.

3. CDC Director Walensky told CNN that we should expect “tens of thousands of breakthrough infections and hundreds of thousands of daily cases.”

Today, let’s try to square the circle of opinions with some data…
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Protection from Hospitalization & Death

In late 2020, when Pfizer applied for its original vaccine Emergency Use Authorization, the company presented clinical trial results that evidenced 90% or better protection against hospitalization and death.

Subsequently, when Pfizer applied for a booster shot EUA, the company presented data indicating that the efficacy of its vaccine in preventing hospitalization only wanes slightly … from around 90% shortly after 2nd shots to about 85% six months later.

Bottom line: high efficacy, slow waning with respect to hospitalizations & deaths.

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That’s a strong commendation for the efficacy (and durability) of the vaccine … but, it’s a relatively weak case for boosters.

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Protection from Infection & Transmission

In 2020, when Pfizer applied for its original vaccine Emergency Use Authorization, the company was silent on protection against infection and transmission.

The simple reason: Their clinical trials didn’t measure whether the vaccines prevented infection and transmission.

Fast forward to 2021 …

In its recent application to get an Emergency Use Authorization for booster shots, Pfizer did submit data indicating that effectiveness against infection starts high (90% immediately after the 2nd shot) …  but it wanes down to around 40% six months later.

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That’s both good news and bad news.

The high initial protection against infection (which is very good news) …  was common-sensically inferred by many … but there wasn’t data to prove it. Now, there’s confirmatory data!

But, there’s also some bad news:

There’s a relatively fast-paced waning of the infection protection (from 90% down to 40%).

That’s a pretty strong case for boosters since any infection brings with it (1) the threat of “long covid” complications (2) the accompanying risk of hospitalization and death (3) the likelihood of transmitting the virus to others.

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About Transmission

More specifically, the data is on point regarding viral transmission … since infection is an obvious prerequisite to transmission.

Early on, soon after people get vaccinated, the risk of infection is very low, so the risk of transmission is very low.

But, as the vaccine’s protection from infection wanes, the transmission risk (among vaccinated people) increases.

The impact is, shall we say, statistically significant.

Tomorrow, we’ll work the numbers….

CDC Director: “Covid vaccines can’t prevent transmission”

October 5, 2021

Now, I’m officially confused.

Yesterday, we posted about a CNBC interview with chief political-scientist Anthony Fauci.

Fauci opined that vaccines prevent covid transmission rates … but when confronted with strong anecdotal evidence to the contrary and asked a pointed question, he conceded that the CDC lacked the data to support that conclusion … but, not to worry the data was likely coming.

New scientific method?

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Drilling down, the CNBC interviewer, Sarah Eisen, read to Fauci from the CDC web site:

“The greatest risk of transmission is among unvaccinated people who are much more likely to get infected, and therefore transmit the virus.

Fully vaccinated people get COVID-19 (known as breakthrough infections) far less often than unvaccinated people.”

That’s when Fauci conceded that the CDC didn’t have the supporting data.

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Despite Fauci’s admission that the CDC didn’t have much data on breakthrough infections, CDC Director Walensky took to the airwaves to proclaim that:

1. Though covid vaccines work “exceptionally well”  against hospitalization and death, they “can’t prevent transmission anymore”. and …

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2. We should expect thousands of breakthrough infections, and …

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3. We might potentially experience several hundred thousand cases a day!

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So, which is it?

> Fauci says not to worry about breakthrough infections if you’re vaccinated

> The CDC web site says not to worry because breakthrough infections are few and far between

> CDC Director Walensky says to expect tens of thousand breakthroughs and hundreds of thousands daily cases … hardly “rare” instances.

It’s hard to follow the science when data is scarce … and  the scientists, who are supposedly reading from the same hymnal, offer widely different “guidance”.

Confusing, right?

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P.S. Note that Walensky’s verbatim was ““can’t prevent transmission anymore”.

Wonder what she meant by “anymore” …

Hmmm


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