You need a doc to order the lab test.

Yes if you are re-infected you will produce abundant antibodies and very quickly. That is the foundation of an immune response. If you are re-exposed but it does not pass your mucosal immunity then your T-cell/humoral system is not activated and you will get an appreciable antibody boost. The feeling of being sick is your immune system activating which is a beautifully complicated series of cytokines and white cell response. It really is amazing when you dig into it.

If your body's immune system is already producing antibodies, more antibodies will be produced when covid is encountered by your immune cells. The cells producing the antibodies will recognize the virus and do what God designed them to do - produce more antibodies.

But, the existence of antibodies is not as important as everyone thinks, and society is way too caught up in the "presence of antibodies". The body's immune system has memory cells - B and T cells - which will recognize the virus if/when encountered again, even if the antibody producing cells are no longer actively producing antibodies. When the B and T cells recognize the virus, a cascade of events occurs and antibodies begin to be produced again by your immune system. The existence of memory cells is what gives us long-term immunity, and there's no reason to think that covid is any different than any other kind of antigen.

And regarding mutations - yes, the virus will mutate. When you have natural immunity against the full virus itself, and not just the spike protein, your immune system can recognize different parts of the virus and cue the production of antibodies or invoke the B-cell and T-cell memory. So as long as some parts of the virus are recognizable to your immune system, your immune system will protect you. As the spike protein mutates away from the alpha variant, vaccine effectiveness declines and may eventually be negligible because all the vaccine does is train your immune system to recognize the alpha spike protein and nothing else on the full virus.

Here's a quote from the article linked below if you want some very technical reading:

"A hallmark of immune responses to pathogens is to create a memory of the response, which is the persistence of small numbers of pathogen-specific B and T cells and the PCs that secrete pathogen-specific Abs. Immune memory may block future infections without symptoms developing either by continued production of neutralizing Abs from long-lived PCs or, if that Ab amount diminishes, by recalling memory B and T cells to rapidly produce new PBs and thus restore high-affinity, neutralizing Abs in circulation."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7826135/

GenericAggie said:

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Then how do people get Covid twice?

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The same way that people get a common cold, the flu or other respiratory viruses time and time again. The virus mutates just a little and you get reinfected, but your immune system recognizes the virus (or parts of the virus) and mounts an attack. You may feel sick for a few days and then you'll get well.

I imagine that the common cold might kill some Amazon tribes who have no natural immunity because they've never been exposed to it. Just like the world had no natural immunity to covid, and thankfully, this is changing one case at a time.