I think the point is, the memory cells do not retain this knowledge for extended periods of time in the case of the current Covid vaccines we have. So should we be looking for a 3rd dose, or try to fund a different vaccine?
Well, that's the question that this study doesn't answer. They (of course) didn't try to infect seniors with reduced antibody response with Covid, they only studied the antibody response in the lab. So the memory cells probably weren't a factor in the lab tests...
When you get infected (or vaccinated), your body produces antibodies as part of its primary response. The antibody tests that are commonly done for COVID look for these already circulating antibodies.
Upon infection or vaccination, your body will also produce antibody-producing memory cells to help respond more quickly if you are infected in the future. If you want to test for these memory cells, you can't use antibody tests. You have to use specialized tests that look specifically for the memory cell responses.
There are some commercially available tests, such as https://www.t-detect.com/, which looks at the T cell response.
A lot of the commercially available antibody tests will fail to detect a prior infection after just a few months. T-Detect now says that its test can pick up infections that occurred 10 months ago. 10 months is probably not the limit of detection; it's just based on the amount of time T-Detect has been available to the public.
Researchers have found memory T cells that respond to the original SARS-CoV virus 17 years post-infection:
Can any tests distinguish between having a response due to prior infection from having a response due to vaccination?
In the months before I was vaccinated I had on two or three occasions something that felt a bit different from the usual cold/flu/allergies that I get, but was not severe enough to justify trying to get a COVID test. I'm curious if I actually have had COVID or not.
It's like saying "All people run out of edible food (antibodies) within hours of being hungry (exposure to distinct protein)". Well, yes, but we have the ingredients to make them in the fridge (memory cells). Just measuring the amount of cooked food (antibodies) will tell you how much I can eat right now, but I'm not going to starve (get sick) in the absence of the cooked food (antibodies) since I have the tools - raw food (memory cells) in case I get hungry (exposed again).
In the case of this study, they tell us we've run out of cooked food in 6 months. That doesn't tell us whether we'll starve, because we could have hella stores in the pantry and they specifically did not measure any of that.
