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Covid-19 Antibody Seroprevalence in Santa Clara County, California

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Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#181

Post by cameldrv »

usaar333 wrote: post #172
cameldrv wrote: post #153

Earlier quoted context omitted.

There was another serological survey of blood donors in Castiglione d'Adda in Italy. That one came up 70% positive. That town had 1.4% of its population die in March. That suggests an IFR of 2%, not counting people who were sick and might die from COVID in April.

We do need to be careful talking about "IFR" as with a disease with such high age-dependence demographic skews heavily alter population IFR. Castiglione d'Adda has more people over 70 than Santa Clara County has over 65; population over 65 is about 60% higher relatively. Population under 18 conversely is about 22% lower. Hard to do the math exactly, but if you simply switch 8.1% of your population from being children…

I agree that you have to make an age adjustment for IFR, and your numbers seem reasonable. However, in the U.S. you also have a lot more diabetes, obesity, and high blood pressure, which are major risk factors. I wouldn't be surprised if that required a bigger adjustment than the age difference.

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#182

Post by nradov »

robotcookies wrote: post #104

"Participants were recruited using Facebook ads targeting a representative sample of the county by demographic and geographic characteristics." How is it representative when it's only Facebook users in this sample?

The link was widely spread around via Nextdoor, email lists, other social networks. You could say it went viral.

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#183

Post by nradov »

terramars wrote: post #71

my friend probably had the virus (2 inconclusive tests) and tried to get into this study. some group asked her for $125 to get tested. i'm not sure if she saw any of the facebook ads. so, grain of salt about representativeness of the sample. there's for sure a response bias towards people who think they had it.

The Stanford study was free. They didn't charge $125.

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#184

Post by usaar333 »

cameldrv wrote: post #181
usaar333 wrote: post #172

Earlier quoted context omitted.

We do need to be careful talking about "IFR" as with a disease with such high age-dependence demographic skews heavily alter population IFR. Castiglione d'Adda has more people over 70 than Santa Clara County has over 65; population over 65 is about 60% higher relatively. Population under 18 conversely is about 22% lower. Hard to do the math exactly, but if you simply switch 8.1% of your population from being children…

I agree that you have to make an age adjustment for IFR, and your numbers seem reasonable. However, in the U.S. you also have a lot more diabetes, obesity, and high blood pressure, which are major risk factors. I wouldn't be surprised if that required a bigger adjustment than the age difference.

Agreed that US as a whole can have a high IFR.

Santa Clara county though is one of the healthiest places in the US. Life expectancy of 84 exceeds Italy in fact.

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#185

Post by fragmede »

contravariant wrote: post #133
MiguelVieira wrote: post #109

Earlier quoted context omitted.

I've been using 0.5% for mental math, rounding down from the lower bound from this study in The Lancet: https://www.thelancet.com/journals/laninf/article/PIIS1473-3... I would be surprised if, after this current wave of infections, the percentage of people with antibodies in the US is higher than the low single digits. Herd immunity without a vaccine is a pipe dream. Our best bet is to massively ramp up testing and c…

Herd immunity isn't a pipe dream it is just one hell of a sacrifice. And we'd better check the immunity actually lasts before we try that. Frankly I've never been a great fan of the 'flatten the curve' explanation, sure the graphs seem nice but I reckon the peak in those graphs is drawn too low by several orders of magnitude. In the Netherlands a fatality rate of 0.5% would mean it'd take about a year for herd immuni…

Let me quantify that sacrifice in a US-centric way with some napkin math to ballpark:

328.2 million (Approximate population of the US [1]) * 80% for herd immunity (based on an R0 5.7 [2]) * 1% = 2.6 million people die.

If the fatality rate is 0.5% instead, then 1.3 million people die If the fatality rate is 0.1%, we're still looking at ~260k-ish people.

That's pretty grim.

This situation is still developing so hopefully those numbers get adjusted downwards as later information becomes available.

For reference, ~1.2 million people died to heart attacks and cancer in 2017. [3]

[1] https://www.census.gov/popclock/ [2] https://wwwnc.cdc.gov/eid/article/26/7/20-0282_article [3] https://www.cdc.gov/nchs/fastats/leading-causes-of-death.htm

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#186

Post by SubiculumCode »

cameldrv wrote: post #180
SubiculumCode wrote: post #177

Earlier quoted context omitted.

3,300 people signed up for this study and completed this within weeks. Have you recruited for a study before? That kind of participation is hard to achieve...practically unheard of, unless you have widespread interest and time: Something which a whole lot of people have right now given layoffs, fear, and the bit of monetary compensation for participation, I bet sampling was much wider and less biased than you think.

Yeah but most studies aren't testing for a virus that has everyone locked in their houses causing a global pandemic.

But that is the point. Selection bias towards those that are actually infected is minimized when a large portion of the population have the time and desire to get tested.

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#187

Post by lern_too_spel »

gryson wrote: post #18

"We recruited participants by placing targeted advertisements on Facebook aimed at residents of Santa Clara County..." I wonder if these ads mentioned the purpose of the study, or if that information was only given out after initial contact (I don't know enough about IRB requirements here). A concern is that this could cause a selection bias for people who suspected they had the virus. People may respond to such an a…

There is also selection bias in whom Facebook will show the ads to due to Facebook's CTR models, other bidders' bids, and who is browsing Facebook more to see more impressions in general. They should have worked with an ad platform to run the ad as a PSA so they could use the ad platform's own randomization instead of relying on having the auctions they win result in anywhere close to a usable sample.

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#188

Post by redis_mlc »

zaroth wrote: post #73
SpicyLemonZest wrote: post #21

Earlier quoted context omitted.

Right, that's why people say the Chinese government's lies (and the WHO's acceptance of them) are at fault. The rest of the world certainly should have reacted sooner, ramping up PPE production and researching treatments and trying to slow it down. But the idea of complete containment, forming widespread green zones where the virus is not merely suppressed but eradicated, probably became impossible as early as Februa…

Well and I say this not even to indite China. Maybe they really and truly believed at the time there wasn’t human transmission. Maybe a virus originating in France or the US would have played out mostly the same way. (I doubt it, but that’s irrelevant) My point was just that with the information we had in December, there was no way politically to enact the extraordinary (and extraordinarily damaging) measures that wo…

Your dates are off.

SARS-2 was circulating outside China in SE Asia before Dec. 15.

BlueDot warned subscribers Dec. 30.

WHO notification was Dec. 31.

Disneyworld Shanghai was closed Jan. 24.

You can't hear anything when you don't listen.

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#189

Post by dmode »

h2odragon wrote: post #3

I think the numbers will coma out to show this ripped through the USA in February; we slammed the barn doors closed well after the horse was gone. Of course that's not the narrative that fits agendas so just like with "why cant we test people?" back then, there will be many official reasons not to look for antibody data and to doubt what data gets gathered.

CA and WA had the earliest cases of COVID,I believe in Jan or early Feb. If this ripped in Feb, why did we not see similar hospitalizations and death rates in CA and WA compared to NY,Italy, Spain, etc ?

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#190

Post by DanBC »

thu2111 wrote: post #158
DanBC wrote: post #60

Earlier quoted context omitted.

Why quote Denmark but ignore Sweden? Sweden are doing what you're calling for, and they have pretty high numbers of deaths.

It's not "pretty high", it's middle of the pack and nowhere near the apocalypse that was supposed to be the outcome of their chosen path.

Deaths per 1m population in Sweden is currently 139. For Denmark it's 58, and for Norway it's 30.
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