You’d also have to consider the fairly high proportion of people exposed to the common cold who don’t catch it - presumably some proportion of those people had some degree of immunity. (If one individual with a cold goes into an office/classroom, what percentage of other people in the office/classroom don’t get sick - 90-95%?)
There is no long term immunity to coronaviruses to date. Otherwise we wouldn’t still have the common cold.
The cold is a coronavirus?
No, the common cold is caused by a range of very different viruses including, coronaviruses, rhino viruses and others. They result in similar symptoms though.
Yes and we don’t die from it usually. Probably because we caught them when young and have some partial immune memory.
Even if that is not the case we probably retain immunity over a number of years to coronavirus strains. People exposed to SARS and MERS maintained abs for a few years at least. As for cellular immunity it needs to be determined.
Since the strains constantly evolve we cannot be immune to the new strains completely anyway. But we retain partial immune responses to them allowing us to stop the virus overwhelming our system before we gear up against it (it seems this is the key risk factors…How long it takes your immune system to generare neutralising abs…It’s a battle of who gets there first …Older people’s immune systems may take longer to churn out the neutralising abs).
It can be a cause.
Or, the Corona virus logically mutates into a less lethal strain.
I’m not confident of the logic here. I think the second sentence implies everybody having full immunity, which isn’t what I’m suggesting.
I mean that individuals within a population seem to have varying susceptibilities to catching the common cold, part of which is presumably attributable to some degree of existing immunity. Otherwise, why do you suppose that only a relatively small proportion of exposed people catch it?
I’m not aware of any evidence of long term immunity.
Yes but that is not directly related to your question of immunity.
Well are we being overwhelmed by any of the four current endemic human coronaviruses. Do you see millions of people getting any of the other four strains at the same time , running through nursing homes like a train on fire?
That answers your question mostly.
Not now, no. In the past, yes, albeit without nursing homes.
Because
A) we have generated plenty of individuals with partial immunity
B) those strains are now infecting us when young
In the future I believe covid19 will do the same,.Infecting us when young and we will be relatively safe when adults but it’s just a prediction, so don’t bet the farm on it .
Long term immunity to coronaviruses is something you believe in. It may be true. I’m not sure so far.
There was possibly a bovine coronavirus that jumped to humans around 1895, later it became one of the ‘harmless’ endemic strains . At the time it was a killer too.
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No it’s a scientific fact from published papers.
Not the same thing. I’ve even told you the facts already about SARS and MERS why are you ignoring that.
Why don’t you research it yourself I’m not spoon-feeding replies to your random assertions. It’s easy to find the research papers. Look up ‘neutralising antibodies persistence coronavirus sars mers’. 
I’m not having a go at you man. I’m trying to learn. However, my immediate attempt at researching throws up this:
…It’s basically what myself and Andrew have been saying.
Partial immunity is likely what is happening. The immune system remembers the virus from last time and whole it can’t stop infection straight off it ramps up much faster preventing symptoms appearing and reducong viral load .
A year later, 14 of the same volunteers came back for another round. Of the nine people who’d become infected with the first exposure, six became infected again, but none developed colds. Moreover, they only shed virus from their noses for a couple of days, compared with an average of five and a half days the first time around. As for the five people who’d resisted infection the first time around, all became infected this time, but only one developed symptoms.
It’s fairly reassuring. I’ve read that most patients die from covid because their neutralising antibody response is too slow, over two weeks…
I’ve also read research regarding persistence of neutralising abs for SARS and MERS , they drop off but often detectable years later.
https://www.journalofinfection.com/article/S0163-4453(20)30781-7/fulltext
Prior SARS-CoV-2 infection is associated with protection against symptomatic reinfection
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