What you need to know about 'original antigenic sin' with fall COVID boosters around the corner

Experts are worried that a phenomenon called “original antigenic sin”—where the immune system becomes strongly tuned to the first strain of a virus it encounters—could limit how well our defenses adapt when new variants of COVID‑19 emerge. They caution that repeatedly boosting with vaccines based on the original virus may “lock in” that immune response and make it harder to mount a fresh, effective defense against significantly altered strains.