[jacquesm]

Yes, it was already mentioned today in the update to parliament here. Apparently - as with other respiratory viral infections - if you don't get it really bad then you may not be immune. That's a pretty fine line there. This would explain some of the more puzzling positive / negative / positive test sequences.

[the_watcher]

> This would explain some of the more puzzling positive / negative / positive test sequences.

It seems far more likely to me that both of these phenomena are explained by higher-than-usual false positive and false negative test rates.

[_wldu]

Researchers are finding that COVID-19 testing has roughly 33% false negatives.

https://www.wsj.com/articles/questions-about-accuracy-of-cor...

The LabCorp test is not FDA cleared or approved and is being used under an emergency act.

"Testing was performed using the cobas(R) SARS-CoV-2 test. This test was developed and its performance characteristics determined by LabCorp Laboratories. This test has not been FDA cleared or approved. This test has been authorized by FDA under an Emergency Use Authorization (EUA). This test is only authorized for the duration of time the declaration that circumstances exist justifying the authorization of the emergency use of in vitro diagnostic tests for detection of SARS-CoV-2 virus and/or diagnosis of COVID-19 infection under section 564(b)(1) of the Act, 21 U.S.C. 360bbb-3(b)(1), unless the authorization is terminated or revoked sooner."

The Quest test is not FDA approved either: https://www.questdiagnostics.com/dms/Documents/covid-19/SARS...

"It is possible for this test to give a negative result that is incorrect (false negative) in some people with COVID-19. This means that you could possibly still have COVID-19 even though the test is negative."

Due to this, it's hard to trust test results. It's a best effort and not perfect.

[vinniejames]

What are the false positives rate?

This would affect death rate calculations

[Symmetry]

A PCR will generally have around a 99% sensitivity and a 95% specificity. That depends on things like the nasal swab going all the way to the back in a deeply uncomfortable way and if they only get the front of the nasal cavity (with Covid-19 in particular) it might be just a 95% sensitivity.

Antibody tests will generally have a much lower sensitivity but can detect whether you had the virus in the past.

[_wldu]

Dr. Fauci said the only thing you can count on are positive test results, so I would assume false positives are much more rare, but I'm not qualified to say. I do think it's safe to discount a negative test result, especially if you also test negative for flu A/B but still have flu like symptoms and difficulty breathing. Hopefully soon, antibody testing will be available and much more accurate.

[BurningFrog]

Half-informed layman questions:

If this 30% recovered don't have antibodies, how did they beat the infection?

Does the immune system have some other mechanism to defat a virus?

Or does the antibody production taper off very fast for some people?

Or can the virus just die out by itself somehow?

[jacquesm]

You beat the infection due to a skirmish between your 'standard' immune system and the virus infected cells. As soon as you get a full-on immune system response there is a change and some more long term effects come into play. Nature tends to be very efficient, engaging an expensive mechanism apparently leads to caching the knowledge so it can be recalled when required, but if the expense outweighs the cost of doing so then it stays on a one-off basis.

The longer you deal with biology the more impressive it all is.

[eli_gottlieb]

That was such a good description of learning/updating in the immune system that I just had to go follow you on Twitter!

[somewhereoutth]

There is the innate immune system, and the adaptive immune system. If I understand correctly pathogen specific antibodies are created by the adaptive immune system, so maybe if the innate deals with the virus quickly the adaptive is not triggered.

There was a good TWIV podcast talking about this.

[nsxwolf]

If your innate immune system beats it, does that mean you're effectively already "immune" and are unlikely to develop serious COVID-19 disease when you catch the virus again, or was it just luck?

[LeoNatan25]

Probably luck. Given a much more potent viral load, it is more than likely the same patient can be infected again.

[nsxwolf]

There just doesn't seem to be any good news anywhere.

[BurningFrog]

That makes sense. I was not aware of the two separate immune systems.

So maybe 30% of people have an "innate" system well geared toward defeating this particular virus. Or/and they had a small exposure.

[megous]

Maybe non-specific immune response was able to kill off the virus early?

[jeffdavis]

That seems weird. The virus makes it through all of your defenses, which seems like the hard part, and then gets beaten once inside?

It's like the Trojan horse coming in, and the soldiers, once inside, getting arrested for tax evasion before they can open the gates.

[jjtheblunt]

I believe being homozygous for the delta32 mutation at the CCR5 gene locus is a possible example about which you ask.

https://en.wikipedia.org/wiki/CCR5

[rumanator]

> Apparently - as with other respiratory viral infections - if you don't get it really bad then you may not be immune.

Source?

[jacquesm]

Start here and keep on reading, it is fascinating stuff.

https://en.wikipedia.org/wiki/Adaptive_immune_system

[rumanator]

I'm not referring the general concept. I've asked for a source that supported the claim that covid19 patients that "don't get it really bad" have been found to not get immune.

[jacquesm]

That was straight from a government hearing today here in NL, those usually don't come with conveniently linked sources but at the same time they tend not to have bullshit in them.

[rumanator]

But do you have a source that backs up your baseless assertion? The world is tired of random guys online saying all type of nonsense and making all sorts of wild claims to then cower behind empty appeals to authority. I can just as easily claim that the pope said to me personally the exact opposite of what you're saying.

[jacquesm]

You are just trying to stir the pot. You could make that claim but you would be lying, and I'm not. I also stake my reputation to this claim and you are an anonymous coward.

You latched on to the wrong part of my comment, the part that was not novel, and now you are moving the goal posts to pretend that it was about the other part of my comment.

Finally, there are several links in this thread and other threads on HN on the subject pointing to articles supporting the novel claim, which you would have found if you really cared, (such as the comment I replied to) rather than that you are just pretending to keep the standard for evidence on HN to your personal level. I have no particular reason to disbelieve a government official making a claim like that in a parliamentary setting. I am not asking you to believe the claim, merely that I am passing it on with high fidelity.

If you choose not to believe that I am fine with it, but I am not in your pay, have given you ample opportunity to study the matter for yourself, no excuse for laziness in the times of wikipedia and the rest of the web, and yet, here you are pretending you have some kind of high ground and using all kinds of slurs. 'baseless assertion' (which it isn't, I've given you my source), 'random guys' (which I'm not, but you are), 'all kinds of nonsense' (this isn't nonsense), 'wild claim' (this isn't a wild claim at all, it is actually quite expected), 'cower' (see any cowering?).

That's a lot of suggestion that you are doing, all of which is trying to shed a negative light on something that is not controversial at all, merely something that you didn't know about yet. Which means you probably don't know all that much about biology to begin with.

It's ok that you didn't know something. It's not ok to not want to then correct that by studying the subject. That's called being lazy. It's not ok to then go harassing people and doing all kinds of borderline namecalling to attempt to pick a fight about something that isn't controversial at all.

So, the coward is you. Now get off your high horse and take it as read that for many viral infections the degree of infection can be to some degree dependent on the initial viral load and that in turn can be a big factor in the development of symptoms and whether or not you will end up immune. The immune system can deal with infections in an ad-hoc manner without invoking its long term planning or it can adapt and guard itself for re-infection in the future. The exact mechanism of the cost optimization is known which you would have understood if you read that WP article I linked to above.

This is NOT controversial at all in biology circles and does not need the kind of support that you are whining for. It's like claiming water is heavier than oil or the nucleus of an atom being larger than an electron, or use of global variables being a bad practice in software development. Pick your analogy.

The novel claim was that this also applies to COVID-19, and that claim is amply sourced.

https://www.medrxiv.org/content/10.1101/2020.03.24.20042382v...

In case you can't be bothered to read the entire pdf, this is the sentence you would be looking for:

"Stronger antibody response was associated with delayed viral clearance and disease severity."

[choeger]

These people came out of hospital. I think they have been hit comparatively hard. I guess (!) we see some result of false-positive test results here, together with coinfection with influenca or even the common flu.

[jacquesm]

Hospital cases are all lower respiratory tract, but even just within that group there is huge variety. It starts from 'under observation' for a day, then goes through needed oxygen for a day or two, to progressively worse symptoms, cytokine storms, intubation, organ failure and finally death, from a couple of different causes, such as lung damage (the vast majority of the cases) or heart failure (1 in 5). It can reverse at any point during that trajectory, and can also go back-and-forth.

And the speed of onset, progression and severity can change dramatically from person to person.

Finally, in many cases of recovery there is apparently lasting damage.

[callumprentice]

Oh interesting and apologies for the repost - I'll go take a look at the comments.