“All we hear about is titers,” says Stephanie Langel, an immunologist at Duke University. That fixation “misses an entire nuance.” Antibodies are supposed to peter out; that’s why they always do. Still, even as our antibodies are dwindling in absolute quantity, these scrappy molecules are enhancing their quality, continuing to replace themselves with new versions that keep improving their ability to bring the virus to heel. Months after vaccination, the average antibody found in the blood simply has higher defensive oomph. “That’s why I hate the word waning,” Jennifer Gommerman, an immunologist at the University of Toronto, told me. “Antibody levels are declining, but something good is happening too: The immune response is evolving.”

The focus on antibody counts alone actually does a disservice to our understanding of immunity, experts told me. Like a block of wood being hewn down into a sharper blade, vaccinated immune systems can hone their skills over time. Part of waning certainly does mean fewer. But it can also mean better.

A couple weeks after vaccination, a group of immune defenders called B cells starts to pump out antibodies en masse. But many of these early antibodies are, as Bhattacharya told me, “really crappy” at their jobs. Their raison d’être is to be clingy—the Y-shaped molecules hook their tips onto a specific hunk of SARS-CoV-2’s anatomy, and hang on for dear life. The better they are at glomming on, the better chance they have of waylaying the threat. Sometimes it’s a solo act: Antibodies alone can grab on so firmly that they block the virus from hacking into a cell, a process called neutralization. Or they’ll use the stems of their Ys to flag down other members of the immune system in a destructive assist.