Imprinting is a quirk of the immune system in which someone’s initial exposure to a virus biases their immune response when they meet the same virus again.

Studies are showing how imprinting shapes people’s responses to SARS-CoV-2; those infected with earlier strains can mount weaker responses to a later Omicron infection.

This phenomenon is dampening the hope that variant-tailored boosters will markedly reduce transmission of the virus, although researchers agree that variant-tailored boosters are worth getting because they still provide some immunity, and prevent serious illness.

This is an audio version of our Feature: How your first brush with COVID warps your immunity

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