"Can't" is too extreme. "Very unlikely" is much more accurate.
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.
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.
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!
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.
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.
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.
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.
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.
The open question is, again, what will be the percentage of such cases.
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.
'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.
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.
In a nutshell, you can't catch it again right away after having recovered.