The emergence of SARS-CoV-2 with the resultant COVID-19 pandemic resulted in the need to rapidly advance vaccine development.  New vaccine technologies, such as mRNA and viral-vectored vaccines, moved rapidly through the various stages of vaccine clinical trials to FDA Emergency Use Authorization within about 9 months of starting their Phase I clinical trial.  Older technologies, such as protein-based vaccines, still have not completed their US Phase 3 clinical trials.  The success of mRNA vaccines in opens the door for applying this technology to currently vaccine-preventable illnesses (e.g., influenza) and other novel vaccine development.  Fundamental basic immunological and clinical questions remain about mRNA vaccine technology that will need to be addressed for this technology to usher in a new era in vaccinology.