1/ Here's another quiz for budding epidemiologists

The Guandong Delta outbreak was meticulously investigated. Initial report of 1000x viral load came from there

A finding that hasn't been discussed much is the seeming shorter incubation period (panel b)

virological.org/t/viral-infect…
2/ In 2021 delta it was only 3.7 days (vs 5.6 days for 2020 outbreak).

This would have an impact on a key transmission dynamic factor we often look for: "serial interval periods" (time between symptom onset for index case vs subsequent case in a contact tracing investigation)
3/ What you are trying to estimate from observable symptom intervals is underlying mean generation time.

tangent: If you find negative serial intervals as in COVID, it's a sign of asymptomatic and presymptomatic spread.
4/ (A household transmission study in Singapore didn't find a difference between delta and wild type covid strains, but was so teeny in sample size that I don't think it really counts as evidence one way or another)
5/ Here's the quiz.

If Delta's incubation period is 34% shorter, and cycles through faster from generation to generation, what would that mean for our estimates of R0?
6/ A plurality of us (34%) got the right answer- If generation time is faster, than means that a lower Ro would explain the growth dynamics

It might seem like a distinction without a difference but it means that a smaller change in behavior (or vaccinations) would reverse trends

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More from @Farzad_MD

31 Jul
Without looking it up,

What is Rt in Arkansas right now?
Rt is actually 1.2 (0.98-1.5). It is taking 12 days (4 generations) to double

here's some math

If Rt (aka Reff) was 5, it would mean that it would go up 5*5*5*5 = 625 TIMES in 12 days, not 2x

epiforecasts.io/covid/posts/su…
3/ Now, we aren't living in an R0 world. Even though it may feel like it sometimes

People are vaccinated (despite breakthrough infections)
People are infected (despite reinfection risk)
People have changed behaviors

But "Delta variant is as transmissible as Chicken Pox"(R0~9)??
Read 8 tweets
30 Jul
1/ Like many others, I've been frustrated that we haven't seen the data behind the CDC's new recommendations. Parsing exact wording in transcripts is🤦

We're told there will be a release tomorrow but thanks to the @washingtonpost there's an internal CDC document to parse tonight
2/ The article by @yabutaleb7 @carolynyjohnson @JoelAchenbach is here:
washingtonpost.com/health/2021/07…

TY @bijans for spotting the "full pdf" download button.
3/ what do we learn?

The mysterious "other data" for high viral load in breakthrough cases came from a 4th of July outbreak in Provincetown (Barnstable, Mass) where the “vast majority” of the new cases were among fully vaccinated individuals

cc @zeynep
thehill.com/homenews/state…
Read 16 tweets
28 Jul
1/ What percent of vaccinated people who get infected with covid will have long-term symptoms?

I don't know, but I highly doubt that it's 19%.

Here's why I say that, and what the *right* study design would be for answering that question.
2/ when I was an Epidemic Intelligence Service Officer at the CDC, I investigated lots of outbreaks, and every one would have a symptom checklist

A surprisingly high number of people with a diagnosed infection will say YES to a variety of symptoms

Fatigue?
Headache?
Fogginess?
3/ many of these reported complaints would have absolutely nothing to do with their infection.

But recall bias is super powerful, and respondents often feel like they're supposed to say "yes". So they do.
Read 7 tweets
7 Jul
1/ Our national quality/value program (MACRA) is broken

Most people just complain about its shortcomings, but @Travis_Broome comes up with an elegant, grounded way to fix its biggest flaws

Apply behavioral economics, use virtual groups, lay path to APMs ajmc.com/view/macra-has…
2/ MACRA was a true milestone, and a concept that I still support- instead of artificially capping medical inflation (and then not having the guts to actually see doc pay cuts) lets create 2 paths- a "pay for performance" base and an incentivized alternative payment model track.
3/ But 3 seemingly technical details fundamentally sapped the potential impact of this huge bill.

classic behavioral economics- the impact of an incentive is not just proportional to its size, but also its cost, uncertainty, and delay

MACRA stunk on all counts here.
Read 14 tweets
19 May
1/ "Federal antitrust oversight has proved inadequate at preventing anticompetitive effects across the health care sector" per @commonwealthfnd

What else can the federal government do, given the difficulty of passing healthcare legislation?

Plenty.
commonwealthfund.org/blog/2021/fede…
2/ in this article, Joseph Kannarkat and I break down all the tools that the Biden administration and @SecBecerra have to address competition beyond antitrust reviews

jamanetwork.com/journals/jama-…
3/ first of all, if the Biden administration chooses to elevate health care competition as a priority, it may garner rare bipartisan support.

This is an issue that has support from left (@ZekeEmanuel) and right (@Avik) thought leaders and legislators.
Read 8 tweets
11 Apr
1/ in our continued COVID field epidemiology series

"What's the question?"

April 2021 edition: "Are the vaccines effective against the variants?"

We have wet lab data, (limited) clinical trials reports, but what about field epi?

What epi design/surveillance would answer it?
2/ Why do I think it's "The Question" of this moment for field epi to try to answer?

I'm going to be joining @Bob_Wachter @cmyeaton @inthebubblepod tomorrow in our continuing "Safe or Not Safe" series, and Variant vs Vaccine will make all the difference

3/ I am 100% certain that everything I am saying here is much better understood by city/state epidemiologists @CSTEnews and @CDCgov experts.

But they are too busy to tweet, aren't free to talk openly, and may not control their own work/ resources.

And that's exactly the problem
Read 16 tweets

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