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Covid-19 Antibody Seroprevalence in Santa Clara County, California

medrxiv.org

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

#61

Post by BearOso »

projektfu wrote: post #49
georgewfraser wrote: post #31

There are now multiple sources of evidence pointing to a very low true infection fatality rate, as low as 0.1% in some regions. Iceland has been testing a semi-random sample using PCR since early in the epidemic, and there have been several small antibody surveys in “hot spots” showing infection rates over 15%. You can also use CDC surveillance of flu-like illnesses to estimate the total number of infected nationwide…

It may have a low overall fatality rate, yet it seems to have a high rate of hospitalization in clinical cases.

And it’s more contagious than the flu, so even if the fatality rate is identical, more people are at risk.

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

#62

Post by ysleepy »

microdrum wrote: post #47
cdelsolar wrote: post #45

Earlier 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…

You are oversimplifying.

While these numbers are indicators, they are non-representative samples. Different communities spread the disease to different demographics.

A CFR of 0.4% is still huge, especially if it is very non-uniform and would mean 1.2mio deaths in the US if it saturates.

And if that isnt enough for you, we still don't have reliable information about long term effects of an infection. It could end up being persistent like herpes or HIV, make people sterile or reduce lung capacity and or increase chance of cancer.

With these, possibly small, risks, it is ethically incredibly irresponsible to allow the disease spread through the whole population. You cannot gamble with a conceivable downside like that.

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

#63

Post by usaar333 »

sxp wrote: post #14

There are similar high infection rates from other semi-randomized samples. https://www.nejm.org/doi/full/10.1056/NEJMc2009316 > Between March 22 and April 4, 2020, a total of 215 pregnant women delivered infants at the New York–Presbyterian Allen Hospital and Columbia University Irving Medical Center . All the women were screened on admission for symptoms of Covid-19. Four women (1.9%) had fever or other symptoms of…

NYC has 30x the per capita death rate of Santa Clara county.

Santa Clara county only being 15% as infected is not consistent.

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

#64

Post by gryson »

compiler-guy wrote: post #50
gryson wrote: post #37

Earlier quoted context omitted.

What adjustments were made to account for selection bias of the sort described? It's not covered in the paper, and "well-established science" certainly doesn't answer the question.

These are very common statistical methods when dealing with surveys and populations. It isn't this paper's job to describe the background on something like that, just like it isn't this papers job to explain blood testing. They describe their limitations and adjustments exactly like most other studies of this sort do. For example: "Those imbalances were partly addressed by weighting our sample population by zip code,…

On the contrary - detecting selection bias of this sort can be very difficult. Do you measure it using a questionnaire? You might ask your subjects "Do you think you previously had COVID-19?" But what do you do with that response data? Exclude everyone that says yes? Then you're skewing one way. There's obviously no population data to match that response with like there is for general demographics such as race and age.

Many studies are only as good as their sampling methods. A good sampling method will alleviate concerns of selection bias.

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

#65

Post by usaar333 »

mgreg wrote: post #17

There's also some data coming out of Wuhan around antibody testing. The methodology is not as well formed as the study in the OP but there is still value in the data. > Wuhan’s Zhongnan Hospital found that 2.4% of its employees and 2% to 3% of recent patients and other visitors, including people tested before returning to work, had developed antibodies, according to senior doctors there. Additional antibody testing i…

It is far more credible that Wuhan hit 3% infection rate (that's about double the PCR testing rate of the evacuees) than Santa Clara county, with an order of magnitude lower death count, having a 2% rate.

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

#66

Post by slg »

MikeAmelung wrote: post #59
slg wrote: post #46

Earlier quoted context omitted.

I'm not sure why we should believe the strain that originated in Wuhan was milder, but lets go with this theory for a minute. How does the nursing home in Washington fit into that picture? It was one of the earliest known hotspots in the US and it was extremely deadly. Was it the mild strain that you think might have already been spreading through California or the severe strain from Europe that spread to Washington…

Not that I necessarily agree with the theory, an influenza outbreak in a nursing home could be extremely deadly. This is why they are nearly 100% vaccinated. And they are (or are supposed to be) quick to quarantine and lockdown if it seems like flu has been detected. Which is to say that even a "mild" strain would certainly pose a larger risk to a nursing home.

I realize that, but it skips over the last question in my previous post. Why didn't we see a similar situation in any California nursing homes if this mild strain was spreading unchecked for months in a population with zero immunity?

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

#67

Post by SpicyLemonZest »

timr wrote: post #54
cdelsolar wrote: post #43

Earlier quoted context omitted.

there is no herd immunity if reinfection can occur, which appears to be the case

There is no credible scientific evidence that reinfection can occur. There have been, at most, anecdotal reports from unreliable sources.

And there are good reasons to believe reinfection shouldn't be possible, to be clear - it's not just being dismissed out of hand.

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

#68

Post by ortusdux »

timr wrote: post #48
ortusdux wrote: post #23

Earlier quoted context omitted.

I keep hearing this sentiment, but I cannot square it with the fact that a non-trivial percent of infected people need to be on ventilators for roughly 20 days. If, back in December, 10k people had what we now know as Covid, there would have been dozens of people on ventilators for weeks at a time in January. The average flu patient needing intubation is only on a ventilator for about 5 days. I just don't see a situa…

All of the flu surveillance numbers suggested a historically bad season this year, and there was a big peak in flu-like mortality in February. It's entirely possible that we were mis-characterizing the data: https://gis.cdc.gov/grasp/fluview/mortality.html

The data from that time period seems to coincide with positive influenza test results:

https://gis.cdc.gov/grasp/fluview/fluportaldashboard.html

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

#69

Post by dsjoerg »

compiler-guy wrote: post #50
gryson wrote: post #37

Earlier quoted context omitted.

What adjustments were made to account for selection bias of the sort described? It's not covered in the paper, and "well-established science" certainly doesn't answer the question.

These are very common statistical methods when dealing with surveys and populations. It isn't this paper's job to describe the background on something like that, just like it isn't this papers job to explain blood testing. They describe their limitations and adjustments exactly like most other studies of this sort do. For example: "Those imbalances were partly addressed by weighting our sample population by zip code,…

Adjusting for selection bias is really hard and potentially first-order.

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

#70

Post by ludwigschubert »

Great 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.

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