Why are the first approved RNA vaccines only available now? After all, they could’ve helped us to combat other infectious diseases in the past. Three recent technical advances make these vaccines possible. First, RNA is unstable and difficult to get inside cells. But by encasing it in molecules known as lipid nanoparticles, delivery and stability have been improved. Second, ‘foreign’ RNA can trigger an immune response (instead of the protein that it helps the body make). But if the RNA is chemically made with synthetic nucleosides, then the immune system doesn’t react against it. Third, RNA is
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