Katherine J. Wu writes:

A new dichotomy has begun dogging the pandemic discourse. With the rise of the über-transmissible Delta variant, experts are saying you’re either going to get vaccinated, or going to get the coronavirus.

For some people—a decent number of us, actually—it’s going to be both.

Coronavirus infections are happening among vaccinated people. They’re going to keep happening as long as the virus is with us, and we’re nowhere close to beating it. When a virus has so thoroughly infiltrated the human population, post-vaccination infections become an arithmetic inevitability. As much as we’d like to think otherwise, being vaccinated does not mean being done with SARS-CoV-2.

Post-vaccination infections, or breakthroughs, might occasionally turn symptomatic, but they aren’t shameful or aberrant. They also aren’t proof that the shots are failing. These cases are, on average, gentler and less symptomatic; faster-resolving, with less virus lingering—and, it appears, less likely to pass the pathogen on. The immunity offered by vaccines works in iterations and gradations, not absolutes. It does not make a person completely impervious to infection. It also does not evaporate when a few microbes breach a body’s barriers. A breakthrough, despite what it might seem, does not cause our defenses to crumble or even break; it does not erase the protection that’s already been built. Rather than setting up fragile and penetrable shields, vaccines reinforce the defenses we already have, so that we can encounter the virus safely and potentially build further upon that protection.

To understand the anatomy of a breakthrough case, it’s helpful to think of the human body as a castle. Deepta Bhattacharya, an immunologist at the University of Arizona, compares immunization to reinforcing such a stronghold against assault. [Continue reading…]