But by the end of 2020, the vaccines that had generated the most excitement used RNA. An RNA vaccine skips the first few steps of a DNA vaccine entirely and induces potent immunity.18 Once inside the cell, it is translated directly into the spike protein which is used by the host cell to build up immune responses. By the end of November, two leading candidate vaccines created by Pfizer and BioNTech and by Moderna that used RNA technology had been shown to be effective after two doses. In December, these candidates were the first two mainstream vaccines approved in the world. The broad use of
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