 Pfizer Inc. PFE, 3.07 and German partner BioNTech SE BNTX, 5.64 said Friday they have received fast track designation from the U.S. Food and Drug Administration for a single-dose-mRNA-based vaccine candidate targeting both COVID and flu. The companies already announced that they are in early-stage trials to review the safety and immunogenicity of their combined vaccine among healthy adults. 