Immunological memory has a few aspects, one of which is like you say the memory B cells, which take over from antibodies after a while. If I'm not mistaken howe

Immunological memory has a few aspects, one of which is like you say the memory B cells, which take over from antibodies after a while. If I'm not mistaken however, there are also long-lived plasma cells which keep producing very low levels of antibodies for decades. In fact, with a single drop of blood, they can figure out every infection you've ever had [0] Still, it's perfectly normal for antibodies to wane after an infection. I'm unsure in general what to make of this study, maybe the number just drops under the limited sensitivity of their test. This study [1] finds that antibodies are stably produced for months after the infection 0: https://www.hhmi.org/news/your-viral-infection-history-single-drop-blood https://www.hhmi.org/news/your-viral-infection-history-singl... 1: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7554472/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7554472/