This is important, and is more evidence that #SARSCoV2 induces a perfectly good immune response. There is every reason to believe that protection will be as long lived compared to other standard immune responses. https://twitter.com/TheBcellArtist/status/1344736754889351174

Yes, many studies have shown that levels of antibodies against #SARSCoV2 antigens fall after the infection is cleared. This one does too. However, THIS IS NORMAL and what we would expect to happen in any text-book immune response.

The key here is that the authors of this study found that a population of the cells that make anti-SARSCoV2 antibodies establishes itself in the bone marrow. This is a very cozy place for these cells, called Plasma Cells (or, once they've moved to the BM, Long-Lived PCs or BMPCs)

- as an aside - yes it is annoying that #immunologists come up with lots of names for the same thing. Sorry.

BMPCs in other immune response are known to live for years and continue to produce antibodies that protect from reinfection.

These antibodies can block infection completely, or they can help get the secondary immune response going much more quickly to fight off a reinfection - often before you even know you are sick. From an immunology perspective, this is very much a win.

The levels of the antibodies definitely remain lower than they were at the height of the primary infection, but they are still at useful levels.

But this is the important point: The immune response to #SARSCoV2 is doing something that is totally normal and expected. In other immune responses, this is a critical part of long-lived immunity, and there is every reason to believe it will be the case here as well.

That's the good news. The bad immunology news is that, in some people, the immune response in #COVID19 does some things that are unexpected, or not at the right time.

This can contribute to severe disease, as explained in this great thread from @VirusesImmunity https://twitter.com/VirusesImmunity/status/1342898958193094656