This is rather interesting. And yes, you did read that correctly: your immune system can suffer from amnesia and forget everything it knows. It is commonly caused by measles – and is a very excellent reason to get your measles vaccination. Other virus can do this too, just not as efficiently as measles.
The measles effect has been known for some years but researchers are now beginning to understand how it works. And contrary to the article “immune amnesia” is not that new. I was effectively told about it by a senior consultant at Hammersmith Hospital back in the early ’80s in the aftermath of having glandular fever. He called it “anamnesia”, the body not forgetting the infection it recently had. But I guess at that time no-one had done any detailed research.
I certainly had measles as a kid – I don’t recall how old I was; but it was before there was a vaccine – but I don’t remember any obvious effects afterwards (nor any of the nasty side-effects of the disease).
And measles is one of our most infectious diseases, with an R number in the range 12-18, so around 3-4 times R for Covid-19. (R is the average number of people someone will infect if they’re contagious.) Which is another reason vaccination is so important.
Here’s the BBC article https://www.bbc.com/future/article/20211112-the-people-with-immune-amnesia – it’s quite a long read and may be a bit too technical in places, so if necessary just take the useful bits.