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Comment by BjoernKW | Hacker News Reader

This is good news because it suggests that immunity for SARS-CoV2 isn't worse than that for other coronaviruses (e.g. those causing the common cold), even for those individuals who didn't become so sick they had to be hospitalised.

In a nutshell, you can't catch it again right away after having recovered.

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>In a nutshell, you can't catch it again right away after having recovered.

"Can't" is too extreme. "Very unlikely" is much more accurate.

Extrapolating from other coronaviruses, it's probably that you CAN catch it again but it's "very unlikely" to produce serious consequences after the first time.

So basically only first time you will experience more serious symptoms like a fever, the subsequent infections would be trivial common cold.

We'll see.

I think we should consider it to be as yet unproven - a person I know through my wife caught it in April (and tested positive them) and wasn't that ill.

They just got very ill again in the last week and tested positive again. Might be totally a-typical or it could just be that we've not seen that many people actually have the chance to catch it twice yet.

Positive with what ? I head PCR stay positive a long time

I'm an absolute layman, but "no worse than the common cold" doesn't sound too great to me since I've always been told you can keep getting the cold over and over again. What am I missing?

There are a lot of different common cold viruses, so catching one doesn't give you immunity for the rest.

(username checks out)

Ah! I knew that this was true for the flu, but I always thought there was just a single Common Cold that you could get over and over again. Thanks!

If you look at the Wikipedia article, you will find more detailed information, but the common cold is caused primarily by rhinoviruses. However, some are also coronaviruses and even influenza viruses. There are hundreds of viruses that cause "the cold."

https://en.m.wikipedia.org/wiki/Common_cold

I think you can get most of them again, but not for a few years.

Here's my understanding (also a layman but trying to read as much as possible):

A new coronavirus jumps from an animal to humans. No human body has seen this type of virus before, so when it infects the immune system has to work a lot to learn how to fight it. This causes symptoms like a fever which is a sign of the ongoing struggle. For frail people it means the immune system is not strong enough to counteract the infection and it spreads and potentially kills them.

However, if the immune system learns quickly enough how to fight it, antibodies are killing the virus faster than it can multiply and you get better. The antibodies then disappear in a few months but the long term memory cells remain.

Later, the virus infects you again. You develop the symptoms of a light respiratory infection but the immune system quickly references the memory cells and is able to produce suitable antibodies really fast. The fight is short and easy, the antibodies defeat the virus before it has time to spread. There is no sign of the struggle like first time (no fever) but only the light symptoms we don't even think of (common cold).

Now, how about children? Well as we see already they're unlikely to be seriously affected (low mortality). And children get lots of fevers (parents can confirm). So probably sometimes in the early years we get infected by some coronaviruses our bodies have never seen, the immune system puts up an intense fight and builds the long-term immunity that will be with us as adults.

There are several coronaviruses that cause what's commonly known as "the cold". If you catch one and recover you're likely to be immune against infections from the same viral strain for some time.

For SARS-CoV2 and the COVID-19 disease it causes this means that even without the - quite likely - availability of a vaccine over time natural immunity will build up within individuals and the population as a whole, which has the potential of both making the resulting disease less severe and future waves spreading less.

If most individuals who contract the virus during the next few months can't get sick anymore and can't spread the virus anymore for the about 6 months those individuals are taken out of the equation, which leaves less individuals for the virus to spread to in the next wave.

> In a nutshell, you can't catch it again right away after having recovered.

If that's the case, out of curiousity why there has been numerous reported cases of people that catched covid again after already recovering from it?

Edit: So... after reading the article I'm not sure this is the case for all people as this research has been done only on a group of asymptomatic & low/mild response people. IMHO for a sentence like that to be valid, it should be demonstrated on the other part of the population, those that have a high immune response against the virus and end up in a critical state from it.

"If that's the case, out of curiousity why there has been numerous reported cases of people that catched covid again after already recovering from it?"

There have been many, many news articles that speculate about this, but to date, I'm aware of two papers that document re-infections. Both papers isolated and sequenced the viruses involved, and both papers documented re-infection with significantly mutated variants of the same virus.

Yes, here is an example of a paper that mentions a re-infection with significant genomic differences between the two samples: https://www.thelancet.com/journals/laninf/article/PIIS1473-3...

No honest scientist would say what you wrote as your “nutshell.” Specifically, T cell response is not equivalent at all to “you can’t catch it.” Still all scenarios are possible: 1) you can still catch it, and still get more sick 2) you can catch it, and be less sick 3) you can be “sterilizingly immune” meaning that you won’t get sick and won’t be able to transmit to somebody else.

But which of those will be by majority the study just didn’t investigate.

In immunology no answer is “yes” or “no” but the range. The range is different between different people, and we can conclude what the typical ranges are, if there’s enough data collected. But the ranges are still unknown at the moment.

The same reason (a need to find the ranges) is why you can’t make a vaccine candidate and be sure how it will work, unless you run big and long enough trials. And that’s why that takes time.

Here’s what this study figured out, quoting from the article: “The size of T cell response differed between individuals, being considerably (50%) higher in people who had experienced symptomatic disease at the time of infection six months previously. Further research will be needed to determine the significance of this finding.”

As you see, again some range, but also not concluding what you claim.

We have been running a "natural" trial on millions of people. From that, we can already tell that reinfection, although possible, is very rare.

I'm not sure we can rule out the idea that reinfection after 6 months is common but almost always asymptomatic in people with healthy immune systems. There was that British common cold coronavirus challenge trial where most subjects could be reinfected after 1 year, confirmed by PCR, but none of them developed symptoms.

Which could mean that such asymptomatic people could still infect somebody vulnerable, if they shed enough virus at some point of their reinfection.

The open question is, again, what will be the percentage of such cases.

Unfortunately there are several taboos on many forums, regarding discussion Covid. For ex.: Covid reinfections, lab origins of covid etc.

SARS-CoV-2 has not been created in the lab. The genome looks completely different than such.

Yeah, exactly what I was talking about. There is no way to say this just by looking at the genome, all you can do is to say that is not very probable, and that would still be a dubious claim. There is a plenty of gnome manipulations that leave no trace. Having said that, lab origin does not neccesarily mean genetic manipulation. Serial passage through animals (say, minks) will leave no trace of genetic engineering, but may make the virus contagius to humans (minks and humans have similar ACE2 receptor). Or just poorly handled sample from the would do.

That are all bogus claims. Biology doesn’t work how somebody not in the field in his simplistic theory think it does. The claims as written show a complete distance from the field and the necessary understanding needed to be able to even understand how wrong the claims are. Theoretically anything can be synthesized, practically, nobody would ever be even near to synthesize what we actually observe. Human controlled “passage through animals” would need many decades to produce the patterns. Totally wrong claims based on bad understanding of how that all works.

How do you identify a lab-created virus?

Of course there is no way. I think people need to start relaxing. Trump has lost, so stop being afraid talking about the lab origins of Covid.

Can we really? Infection itself is still somewhat uncommon, thanks to the global reaction to the pandemic.

I don't doubt that reinfection will be rare, at least over the span of a few months, but to my mind that would seem unproven given how hard we're (generally) working to keep people from being infected in the first place.

In many countries, healthcare workers are exposed (to varying degrees) on a daily basis.

Yes ... and they are getting reinfected. The fatality rate among medics is quite high relative to general population

The fatality rate among medics is quite high relative to general population

'Quite high' could mean anything, but if you're implying 'higher than' then that isn't supported by the statistics I've seen in a dozen countries.

Good point. I'd hope they'd receive regular testing as well.

Unfortunately, your hope is unfounded. My spouse is a physician and when coughing (acute bronchitis) could not get a test without job consequences (being forced to take 10 days off and reschedule all patients regardless of the outcome of the test). There has been an exposure in a neighboring ward through a fellow healthcare worker and tests are not being made available broadly. Remember, in the US healthcare workers generally have to go through insurance to get approved for tests, etc., even though they work in healthcare -- they're not at this time provided anything more than the general public in terms of diagnostics. (At least spouse gets free masks at work, haha...)

Do you know how academic, narrow and unpractically stiff are criteria for a proof of reinfection? You need to have the viral genome sequenced TWO times, and both times it must be a slightly DIFFERENT virus. In that context "very rare" is not a useful term.

There is a temporal component here. As an ancestor commenter said, "you can't catch it again right away" (emphasis added). We do not know (because we cannot know) if reinfection is possible after two years, for instance, because we have not had the virus for two years yet.

Don’t forget there are lifestyle factors that can effect your immune response. You’ll typically fight off a cold except for that one time when it catches you tired, or stressed ...

> From that, we can already tell that reinfection, although possible, is very rare.

No. From the current papers, we just know that the reinfection where people have had their virus sequenced in both first and second infection is very rare.

The problem is technological. Up to now there are around 50 million confirmed cases in the world but probably less than 100 thousand sequencings performed, and only a few sequencings by those who had strong enough symptoms twice and had the chance to have sequencing twice.

Without sequencing one just can’t prove that some case is an actual reinfection. All other cases are just “possible” (i.e. unprovable) reinfections and nobody can claim anything worthy of a scientific paper about them.

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