[nudephil (OP)]

Sally asks:

I have had COVID-19 and I am assuming I will have some immunity for a while, but with it being a coronavirus this will wane over time. With my antibodies still in tip top shape, would it be a good idea to be reinfected with the virus to enable a new immune response that will perpetuate the first one? Or does using the real virus that's still potent bring on a different response than a vaccine that's a altered virus?

So far I have not heard of anyone getting COVID twice, but my understanding is that some coronaviruses can be caught multiple times as the body can forget them from a immunological point of view. I hope that will not be the case with COVID.

Can anyone provide an answer?

[alancalverd]

Some vaccines, and therefore some infections, apparently produce lifelong immunity, and some immunities even seem to be transmitted in breast milk, but some need "topping up".

COVID-19 is relatively new to humans and I think the honest answer at this stage must be "don't know".

[set fair]

Good question. It could be investigated by weekly checks of antibody levels of medical staff who've had covid and work on a covid ward. Rises in anyibody levels would suggest a reinfection fought off.

[alancalverd]

Interesting answer, SF. It raises the question of what do we mean by infection!

We are daily assaulted by all sorts of invaders, most of which are repelled by some reaction or other before they significantly impair our overall function, so there are fluctuations in all sorts of histamine and antibody levels but we don't consider ourselves infected just because one rises a bit. I think infection requires that the invader is replicating faster than we can respond.

So all we will learn from measuring antibody levels in someone who has recovered from but continues to be exposed to a pathogen, is their level of recent exposure. However that may also be a measure of their infective capacity to others: if I'm winning the internal battle but still exhaling viable virus, I might infect someone whose immune system is not yet primed to respond.

[evan_au]

It is true that other coronaviruses are endemic, and come back every year or three. They don't seem to kill many people, so we just lump them in with the common cold as a nuisance, but nothing to be worried about.

It is quite possible that when these cornaviruses were new to humans that they killed a few percent of people - but anyone who was genetically susceptible to those viruses is now dead.

I like to think that we have higher aspirations now - that we would like to prevent a virus killing a few percent of the population.
- In this particular case, it mainly affects older individuals, so the viral infection won't eliminate genetically susceptible genes from the population
- Without a sustained immunity, the more susceptible individuals will get older, and then perhaps succumb to this virus.

This immunity could be sustained by from booster shots, or through enough virus exposure to keep antibody levels high, and killer cells on the prowl (as suggested by the OP).

measuring antibody levels

I have heard of tests that measure immunity via antibody levels.

But killer cells can also be effective even with low levels of antibody.

Has anyone seen any tests to detect levels of killer cell activity against coronavirus?
This paper tries to measure total levels of various antiviral immune responses, including natural killer cells:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7292949/

the honest answer at this stage must be "don't know".

Some of the coronavirus vaccine approaches are quite new - this may be the first time that RNA vaccines have been widely used in humans.

Whether they will produce a more effective immunity remains to be seen. Or maybe susceptible individuals will just need annual booster shots...