You are likely looking for the research done on flu vaccinations. From 2017 https://www.flagshippioneering.com/press/moderna-announces-positive-interim-phase-1

You are likely looking for the research done on flu vaccinations. From 2017 https://www.flagshippioneering.com/press/moderna-announces-positive-interim-phase-1-clinical-data-demonstrating-first-mrna-vaccine-candidate-mrna-1440-induces-high-levels-immunogenicity https://www.flagshippioneering.com/press/moderna-announces-p... And also from 2017 Safety, Reactogenicity, and Immunogenicity of mRNA-1653 in Healthy Adults https://clinicaltrials.gov/ct2/show/NCT03392389 https://clinicaltrials.gov/ct2/show/NCT03392389 The research and testing for mRNA had been a decade in the making and was already present in 2019.