Preliminary test results suggest 21% of NYC residents have Covid antibodies • Hacker News Board

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#421

Post by badfrog » Thu, Apr 23, 2020, 10:11 PM UTC

guscost wrote: post #419

badfrog wrote: post #394

Earlier quoted context omitted.

> New York City had the highest positive rate at 21.2%. The potential good news to come to light is that the death rate may be far lower than some estimates, at 0.5%. How do they get to 0.5%? According to NYC data if you include "probable" cases, 15,400 people, or 0.18% of the population, are already dead. Wouldn't that imply 0.9% fatalities if the whole city was infected?

It would not be ruled as a significant factor leading to death in many of those cases, and for the rest, NYC residents might be more at risk due to higher average viral dose (subways). Also there is a lag in IgG antibody production, the test has imperfect sensitivity, and some portion of exposed people may never develop detectable antibodies. Some of these confounding variables are probably baked into the estimate.

> some portion of exposed people may never develop detectable antibodies.

Interesting. Would those people still develop some form of immunity/resistance?

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#422

Post by guscost » Thu, Apr 23, 2020, 10:12 PM UTC

badfrog wrote: post #421

guscost wrote: post #419

Earlier quoted context omitted.

It would not be ruled as a significant factor leading to death in many of those cases, and for the rest, NYC residents might be more at risk due to higher average viral dose (subways). Also there is a lag in IgG antibody production, the test has imperfect sensitivity, and some portion of exposed people may never develop detectable antibodies. Some of these confounding variables are probably baked into the estimate.

> some portion of exposed people may never develop detectable antibodies. Interesting. Would those people still develop some form of immunity/resistance?

I think so, but I'm not an expert. See discussion: https://news.ycombinator.com/item?id=22958660

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#423

Post by zaroth » Thu, Apr 23, 2020, 10:12 PM UTC

hcknwscommenter wrote: post #375

zaroth wrote: post #357

Earlier quoted context omitted.

According to the CDC, the estimated prevalence of symptomatic flu last year was 45 million illnesses and 61,000 deaths. For NY, assuming it’s evenly distributed, that would translate into 13.8% of 20 million = 2.8m symptomatic flu cases and 3,753 deaths. COVID appears to be significantly more prevalent (roughly twice as prevalent in just 3 months as flu gets all year despite incredible efforts), and roughly 2-3x as f…

I think you need to rethink essentially all of your assumptions/math. COVID is not more prevalent than the flu and certainly more than slightly more fatal.

20% infection rates already puts SARS-CoV-2 at higher prevalence than the flu. And we're barely a couple months into the time period of significant spread.

Why would you think that SARS-CoV-2 would not be more prevalent than the flu? The fact that we have no natural immunity, combined with how virulent it is, indicates the endpoint infection rate will be significantly higher than an average flu season.

"In the U.S., for example, in recent years about 8.3% of the total population get sick from flu each season, a CDC study found; including people who carry the flu virus but show no symptoms, that estimate ranges to up to 20%."

The endpoint percentage of fatalities is a multiple of the infection rate times the fatality rate. Both numbers are equally important.

We've been hearing the "10% hospitalization" and low-single digit CFR numbers for months. At 20% prevalence, the NYC actually had 1.7 million cases, 36,723 hospitalizations, for a hospitalization rate of ~2.1%.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#424

Post by mynegation » Thu, Apr 23, 2020, 10:12 PM UTC

slg wrote: post #386

CubsFan1060 wrote: post #370

Earlier quoted context omitted.

I don't think this a binary outcome. Getting closer to herd immunity also makes things better. Take NYC. Now 1 out of 5 people you see can't infect you (assuming having antibodies means immunity). The closer we get, the better it is. Having 21% "immune" leads to far different outcomes than .1%.

I'm no expert here, so someone can correct me if I am wrong. But I believe as long as each infected person spreads it to more than 1 other non-infected person the disease will continue to spread until there is a herd immunity level of infections. That spread rate will decrease as more people have antibodies, but it seems unlikely to get below 1 since even all the stay at home orders haven't been able to get that numb…

Sustained spread of the infection stops when percentage of people having immunity is 1-1/R0. So if R0 for Covid-19 is (hypothetically) 3, you need 67% immunity to reach herd immunity. For highly contagious diseases like smallpox that number is very close to 100%

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#425

Post by cma » Thu, Apr 23, 2020, 10:12 PM UTC

taeric wrote: post #241

cma wrote: post #211

Earlier quoted context omitted.

We're looking at per capita rates though so doesn't matter if they have more of something in absolute terms.

Could. If the agitating factor to severe cases is car exhaust, as an example. There are usually tipping points to that kind of thing. Look, I agree that I don't know. Just trying to get that uncertainty in the counter claims, as well.

I’m talking about having more number of nursing homes because they have “more of everything”, not making an argument about density and pollution or anything like that.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#426

Post by schrodinger » Thu, Apr 23, 2020, 10:14 PM UTC

badfrog wrote: post #394

aazaa wrote: post #317

> In his press conference today, Governor Cuomo revealed the preliminary results of a first-phase antibody test that surveyed 3,000 New Yorkers over two days in 19 counties at 40 locations that included grocery and big-box stores. The sample suggests that 13.9% of New York State residents have the antibodies, meaning they had the virus at one point and recovered. Of the regions tested–Long Island, NYC, Westchester/Ro…

> New York City had the highest positive rate at 21.2%. The potential good news to come to light is that the death rate may be far lower than some estimates, at 0.5%. How do they get to 0.5%? According to NYC data if you include "probable" cases, 15,400 people, or 0.18% of the population, are already dead. Wouldn't that imply 0.9% fatalities if the whole city was infected?

Maybe that’s including the large number of deaths that are presumed COVID but weren’t officially confirmed by a test?

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#427

Post by zamfi » Thu, Apr 23, 2020, 10:14 PM UTC

TheBlight wrote: post #420

monadic2 wrote: post #418

Earlier quoted context omitted.

> Sure all of these studies are potentially flawed but they're all generally pointing in the same direction. How on earth could you differentiate this from the sample bias?

All three studies created their sample groups differently. Are all three methods flawed in some way? Sure. Is it more reasonable to completely ignore the picture all three are painting or to consider there might be something to the trend?

> Are all three methods flawed in some way? Sure.

They're not just all flawed in some way -- along at least one dimension they are flawed in the same way, that is, they all have a biased sample of the population that seems more likely to be infected than a true random sample.

So, sure, they're "created differently", i.e., they're not all facebook ads, or grocery stores, but all those methods bias towards higher infection rates, don't they?

Given that, you'd expect high precision, low accuracy -- these tests all paint a trend for sure, but we don't know how close that trend is to reality.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#428

Post by cozzyd » Thu, Apr 23, 2020, 10:14 PM UTC

newacct583 wrote: post #345

arrrg wrote: post #334

Earlier quoted context omitted.

The death rate of 0.5% falls right in the range of what modelers have been using, by the way. Not exactly very positive news.

Right. Really this study is just confirming (with higher error bars than we'd like) what we already strongly suspected. Note that as others are pointing out, that 0.5% isn't really extrapolated correctly. The tested case deaths are looking like they're only 70% of the total or so. Also using a current death count with contemporary infection counts is a mismatch, because it forgets that ~35% of the people currently in…

IFR, not CFR

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#429

Post by mlyle » Thu, Apr 23, 2020, 10:14 PM UTC

slg wrote: post #405

TheBlight wrote: post #396

Earlier quoted context omitted.

See: https://www.cdc.gov/flu/about/burden/2018-2019.html Search for "Table 1: Estimated influenza disease burden, by age group — United States, 2018-2019 influenza season"

I skimmed through that so please point it out if I missed it, but the numbers don't seem to account for comorbidities. The question was whether COVID-19 is more dangerous than the flu to healthy young people not all young people.

Just because you've not heard about it, doesn't mean it doesn't happen. Seemingly healthy young people die from the flu each year.

Since Feb 1, 204 people from 15-34 have been confirmed to have died from COVID-19 in the US. 162 people from age 15-34 have been confirmed to have died from influenza in the same period.

I don't think you'll find either statistic broken down by comorbidities.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#430

Post by CydeWeys » Thu, Apr 23, 2020, 10:15 PM UTC

aazaa wrote: post #317

> In his press conference today, Governor Cuomo revealed the preliminary results of a first-phase antibody test that surveyed 3,000 New Yorkers over two days in 19 counties at 40 locations that included grocery and big-box stores. The sample suggests that 13.9% of New York State residents have the antibodies, meaning they had the virus at one point and recovered. Of the regions tested–Long Island, NYC, Westchester/Ro…

> This still is not a random sampling. It only samples from shoppers at grocery stores and big-box retailers. Imagine doing the same study, but of people who ordered groceries online only. Would you expect to see big differences in exposure rate? I think so.

There's a larger, related problem with this: It's way over-sampling people who go outside a lot and make unnecessary trips, and undersampling people who don't. I'm in NYC and I'm only going to one store a week (the grocery store). So I'd have much less chance of being included in this study than someone who hasn't changed their habits and is still shopping much more frequently. And there's a direct correlation between how often you're going shopping and how likely you are to have been exposed to COVID-19.

So yeah, it's very far from a random sampling, and it is specifically over-sampling people who are more at risk. So I'd take it with a grain of salt; it could actually be way off.

They should've activated the jury selection tool for this and gone to people's apartments to draw blood. That way they'd correctly sample the people who aren't leaving home at all, or only do so rarely.