Studies done 9 months after having Covid, 96% had robust anti-bodies and 4% had trace/ample amounts. The “T” cells also go into action quickly as well later on down the road.
However, variants (depending how much it changes) could vary from zero symptoms to cold like symptoms....but we just don’t know enough about the “variants”.
“The researchers first isolated antibodies that could bind to the receptor binding domain (RBD), a crucial region on the virus’s spike protein. They then tested whether the antibodies could neutralize SARS-CoV-2—that is, bind to the virus and stop infection.
[edit: $$$ to do this. Not feasible for the masses]
Most participants had low or very low levels of antibodies against SARS-CoV-2. Only 1% of the study participants had high levels of antibodies that could neutralize the virus.
[edit: this contradicts your remark, “Studies done 9 months after having Covid, 96% had robust anti-bodies and 4% had trace/ample amounts.” Where is your study you quoted?]
To examine the range of antibodies made, the researchers isolated the cells that produce antibodies—memory B cells—from the plasma of six selected participants with very high to moderate levels of neutralizing antibodies. Even in those with modest neutralizing activity in their plasma, the team found potent antibodies against the SARS-CoV-2 RBD. Surprisingly, neutralizing antibodies from different people showed remarkable similarity.”
[edit: As I said in my original comment. Look hard enough,spend time and money,and you will find the memory cells still active. But not feasible for the masses, unless you are prepared to spend billions and have 9 months andtons of dedicated equipment and lab personnel]