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.
Covid-19 Antibody Seroprevalence in Santa Clara County, California
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Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California
#72With only 30 people in the negative control group, the confidence interval on the false positive rate would easily swamp out the results of the study for 1.5% positive sample ratio, no?
Seems kind of useless unless your control group is a lot larger, and the false positive rate can be shown to be <<1.5%.
Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California
#73Earlier quoted context omitted.
That was back when China was claiming it didn’t transmit between humans, and ordering labs to destroy their samples. https://www.nationalreview.com/the-morning-jolt/chinas-devas...
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 would have been required to prevent an epidemic.
Not only was it politically untenable (Trump was only acquitted on February 5th!) but it was simply scientifically unsupported and unjustifiable at that time.
IMO even with hindsight being 20/20 I can’t say given the information we had on January 1 that we could or should have done any differently than the travel ban on January 31st, which itself was extraordinary. Everything post January 31st however is an absolute boondoggle of the highest degree.
As far as PPE and testing capacity, I believe those are both systemic issues which needed to be dealt with years ago. Good luck with the US trying to procure a billion masks from China right at the onset of their own health crisis — imagine how that would play out with 1,000s of deaths in Wuhan and 0 known cases in the US. We would have been accused of hoarding and causing the spread in China.
The testing issue was mainly an easily foreseeable and preventable regulatory problem at the FDA which has existed for some time. It took too long to remove the regulatory hurdles, but that there was not already a pandemic regulatory response framework ready to activate is totally inexcusable since we already went through this in 2009.
Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California
#74Add this to growing pile of evidence that this coronavirus is more widespread than most testing to date would suggest. How much more widespread still appears very unclear. There is a major ramping up of antibody testing happening right now, and multiple new tests being introduced, so we should have a better idea very soon. But the takeaway should be that this is a good thing. Every unknown case we uncover decreases t…
I don't follow your argument. If the epidemic is more widespread than initially thought, why do you assume that the effective transmission rate would potentially decrease? If anything, the transmission rate was higher than assumed and, due to the higher number of infections and how they spread exponentially,it would only ramp up. And additionally, there are reports of reinfections among covid19 patients who were foun…
It's the difference between the effective reproductive rate and the basic reproductive rate. Yes, more cases means a higher basic reproductive rate, which is an innate characteristic of the virus. But more immunity in the world means a lower effective reproductive rate, which is the same rate we're trying to manipulate with physical distancing and masks, etc.
"And additionally, there are reports of reinfections among covid19 patients who were found to be cured."
Like I said in my comment, it is still unclear how immunity works.
Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California
#75Great to see actual testing on a representative population sample, though I’m not sure what the consequences ought to be: > These prevalence estimates represent a range between 48,000 and 81,000 people infected in Santa Clara County by early April, 50-85-fold more than the number of confirmed cases.
So with 69 deaths so far and 9 deaths last week in Santa Clara County, projecting that to an extra 4 weeks to 105 deaths for those infected in early April, that means a 0.16% death rate?
Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California
#76Earlier quoted context omitted.
nope.
Yep. You've got nothing. CFR is low, and this has been knowable for a long time. You're scared. It's OK. It's illogical and anti-scientific, but it's OK. But you won't be able to hurt ordinary people any longer. Here's Germany's imputed CFR: https://spectator.us/covid-antibody-test-german-town-shows-1... Here's Denmark: https://www.dr.dk/nyheder/indland/doedelighed-skal-formentli... Here's Iceland: https://reason.com…
Few non-peer reviewed papers with biased samples, questionable tests and questionable methodology don't make strong evidence. CFR just can't be that low. There are towns in Italy where the virus killed 1% of total population
https://www.ecodibergamo.it/stories/valle-brembana/il-grido-...
Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California
#77I made this comment the last time a serological testing study came out: they have 30 negative controls and claim 1.5% positives among their tests. So the number of controls is insufficient to rule out this being entirely false positives. You have to then rely on the test manufacturer's claims of false positives rates, which comes from 371 negative controls. They say: > our estimates of specificity are 99.5% (95 CI 98…
This (I think?). I am not a doctor or biologist. Anyone who knows more than me, which is not a high bar, please step in and correct me.
Based on quick amateur reading of the paper, the rate of crude positives (1.5%) might be entirely real cases, entirely false positives, or anywhere in between. The real rate of infection could be anywhere from 0% to 5%.
The authors report around 3,500 real tests and 30 known-negative tests. We need 30,000 real data points (or 300 known-negative tests) to conclude anything. (Right?)
I am not criticizing the experts who conducted the study. Thank you for doing the study. I'm only trying to understand what the study reveals. It may reveal that the group needs 10x more funding right away.
Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California
#78I don't see anything about sampling bias here. I would assume that people who have been ill, experienced mild symptoms, or who were exposed to confirmed cases would be more likely to respond to the facebook ads recruiting testing volunteers.
I'm sure we are significantly undercounting cases but I highly doubt we are off by a magnitude of 50x.
Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California
#79It’s hacky and I’m happy to be told how wrong it is. But based on these recent antibody studies in Germany, Finland, and now here in CA, I’ve been assuming an actual fatality rate of about 0.4, and thus an actual infected rate of 250x our known deaths, which is a much firmer number.
This is only a small comfort since it means we may have had about 8.75 million infected and presumably now immune in the USA. Or about 2.6%. There’s still a long way to go in that case.
Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California
#80Antibody tests are not as accurate as RT-PCR, but the sensitivity that was observed here was 91% and 99% specificity when compared to confirmed COVID cases. I just want to point out that these researchers are using the corrects tests to do this.