Reinfection/breakthrough is exactly in line with what the parent poster is claiming, which is that it is due to antibodies waning naturally, either from vaccine

Reinfection/breakthrough is exactly in line with what the parent poster is claiming, which is that it is due to antibodies waning naturally, either from vaccines or from natural infection. However, the B-cells remain and continue to recognize SARS-CoV-2 antigens, causing a rapid production of neutralizing antibodies within hours, as opposed to close to a week in the natural infection case. This leads to greatly reduced hospitalizations.