This seems to be Delta's calling card in high-vax areas. It hits with a big splash - a whole bunch of breakthroughs at once. In this case, SF hospital workers. The test now is to see if there are lots of secondary transmissions from these breakthroughs nytimes.com/2021/07/31/us/…
The vaccine already did its job in preventing serious outcomes - only two of the infected had to be hospitalized. But the secondary transmission question in light of the "comparable viral load" data will be interesting to watch.
And yes, they were wearing masks too. As I tried to calculate this morning, masks add about four points of extra protection to those already vaccinated. So that's 80 points for the vax and 4 for the mask. Delta can top that in a splash.
So this is what endemicity looks like. San Francisco has done a phenomenal job vaccinating 69% of ALL residents and 76% of all adults. They've kept cases, hospitalizations and deaths down throughout as well. But breakthroughs will still happen. And they will almost all be minor.
For those places with lower vaccination rates, it is still very much a pandemic. Those Delta splashes are transmitting from non-immune to non-immune, week after week. And increasing hospitalization, esp. among unvaccinated 40-49s who didn't think they were vulnerable.

• • •

Missing some Tweet in this thread? You can try to force a refresh
 

Keep Current with Aaron Astor

Aaron Astor Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @AstorAaron

1 Aug
Of all the covid metrics out there, I think the most useful right now are hospital admissions for 40-49s. That seems to be the age group hit hardest compared to earlier waves, bc over 50s are more likely to be vaccinated everywhere. CDC tracks them here. covid.cdc.gov/covid-data-tra…
Here are four states experiencing high or recent "case" increases. Compare the 40-49 hosp admissions: Missouri, Louisiana, Massachusetts and Illinois
The worst is Florida. 7.73 per 100k at that age group is horrible. In every state this metric is climbing a bit. FL's vax numbers are average, not low. Only in states with very high vaccination rates for younger and middle age adults will the UK-style decoupling happen.
Read 9 tweets
1 Aug
There is an emotional component to child covid vaccination that is hard to channel through rational risk assessment. No matter how low the actual risk of covid to healthy kids, a HUGE number of parents will not feel comfortable until their under 12s can get vaccinated.
None of this should ever mean that in-person schooling should be curtailed in the slightest. The actual risk comes nowhere near justifying destructive school closures. But I can guarantee you that the tension over this will dissipate quickly when child vax is available.
If you aren't a parent of kids under 12, it's hard to appreciate what this is like. I have three kids under 12. We were in school in-person all year last year. Good safety and communication measures kept cases down in our schools here. But it was still nerve-wracking.
Read 6 tweets
31 Jul
And just like that, we get a key piece of the viral load puzzle from a new study! Breakthroughs and non-vax viral loads are indeed comparable...AT FIRST. But with vaxxed, the loads drop much faster as antibodies kick in. Huge effect on transmissibility! medrxiv.org/content/10.110…
This is the first study of "virological kinetics," or the decline of of viral load, in breakthrough cases. So it is really important for assessing how transmissible breakthroughs are. And as suspected, it shows a real but brief contagiousness window for breakthroughs.
This chart lays it out. Remember that lower Ct means more virus. The relationship to transmissibility isn't entirely clear or perfect, i.e. not sure if the days exactly correspond to contagiousness. But it's clear that breakthroughs drop out of contagiousness much faster.
Read 6 tweets
31 Jul
So there is more evidentiary backing for the comparable viral load claim than P-Town Bear Week. Would have been nice if CDC led with this Wisconsin study instead. But it also doesn't measure duration of high viral load, which is important re: asymptomatic. medrxiv.org/content/10.110…
That symptomatic breakthroughs can spread the virus shouldn't be news to anybody. The real question is whether asymptomatic breakthroughs can spread it. But the contagiousness window closes faster in breakthroughs - probably cutting it to a day or two - as antibodies get to work.
This is probably why high-vaccinated areas sometimes experience a big Delta splash, with lots of breakthroughs at once. But the transmission chain ends soon afterward as each vaxxed social contact is less likely to be infected at all. Vaxxed usually hang around other vaxxed.
Read 5 tweets
31 Jul
Let's think about what extra protection masks can provide for vaccinated people who want to protect their own under-12 kids at home. The CDC slide said masks give 40-60% source protection and 20-30% for personal protection. So this is the latter.
These numbers are wild guesswork. But remember that CDC is recommending masks in high transmission areas, so the personal protection is probably going to be on the lower end. Let's use the 20% number. For vaccines, let's assume they prevent 80% of all infections.
Both of those figures are reasonable for Delta on the average. Masks are supposed to provide "layered" protection on top of vaccines. So that means the 20% protection from masks can apply to that 20% that vaccines don't prevent - i.e. 20% * 20%. Which is... 4 more points.
Read 13 tweets
30 Jul
I don't think the CDC could possibly have selected a less representative sample to measure viral load and justify post-vax masking than "Bear Week" in Provincetown. Their two pieces of evidence were an Indian study based on non-US approved vaccines and...this.
The "viral load" data is so obviously skewed by the peculiarities of this situation that CDC should drop its bullshit panic talk about post-vax superspreaders. Yes, breakthroughs can transmit. We knew that! I'm sure *some* are superspreaders too! But that's it! Such an own-goal.
And now there is a bit more representative data out of Wisconsin to back the viral load claim. CDC would have been better served to lead with this instead. Of course, the consequences are still not "game changing." medrxiv.org/content/10.110…
Read 4 tweets

Did Thread Reader help you today?

Support us! We are indie developers!


This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!

:(