When Drew Weissman first started injecting mice with genetic molecules called messenger RNA, it did not go well. Many of the animals became overwhelmed with harmful inflammation, and some died.
But Weissman solved that problem with a bit of clever biochemistry 15 years ago, working with then-colleague Katalin Karikó at the University of Pennsylvania. Now their work forms the backbone of two vaccines for COVID-19, including the one for which dramatic early results were announced this week.