Thread by @MichaelRosenYes

1/ The immunity principle works on the basis that a person produces enough antibodies to consume the virus and the body retains the capacity to produce these specific antibodies should more of that virus enter the body.

2/ The problem with e.g. the polio virus was that it even though some people seem to have immunity, a socially unacceptable number of people did not. The 'herd' did not produce enough people who were immune. Only the vaccine which artificially produces immunity...

3/ ...cut the 'success' of the polio virus down and in many countries 'out'. The vaccine works on the basis of creating a 'false infection' ie very mild, but the person produces the antibodies which then in most cases are there in the body should some polio virus turn up.

4/ There is a problem though that some viruses are brilliant at mutating - partly because their means of reproduction is open to 'false replication'. This means that the antibodies you have won't work and you have to make a new kind.

5/ The whole notion of 'herd immunity' works on the basis that this infection is a) mild enough not to kill b) humans ca produce antibodies to kill it off in the body and c) these antibodies will work if the person is re-infected and d) the virus won't mutate soon.

6/ the assumption being made is that for under 70s the immune system is working well, and people are producing antibodies which kill it off.However, this doesn't provide immunity to the over 70s! The only thing that will give them immunity is to not mix with other infected people

7/ Immunity can't jump from an immune person to a person who has no immunity just by hanging out with them. Ironically, it may cause more problems in that an infected but immune person (successfully defeating the virus) may give an over70 the illusion that they are safe.

8/ However a vaccine might be produced, it would be hoped that it would provide immunity for most people, with the proviso that a) it may not be 100% universally effective and b) these viruses have their own evolutionary path, and as a result of their mutations are successful.

9/ It's theoretically possible that there are people who are genetically immune to this virus e.g. best able genetically to produce the antibodies that will consume this virus and/or that their bodies are an environment in which this virus does not thrive.

10/ Sometimes in nature there are surprising links between one genetic condition and another where one inherited feature comes linked to another and so enables the body to better cope with a foreign agent.

11/ With such huge numbers of being infected, it may be that surprising linkages or immunities are discovered and you can bet for certain that medics will try as fast as they can to see if these are 'reproducible' in the form of vaccines or medicines.

12/ The other route is to 'inhibit' the actions of the virus as with antiretroviral drugs. So you don't get 'immunity' you block how they invade cells etc. Here's an article explaining how they work.
en.wikipedia.org/wiki/Managemen…

13/ It's possible that medics will create antiretroviral drugs over time to reduce the effectiveness and lethality of coronaviruses. Obvs, these aren't available yet.