Developing vaccines within eggs or cells can take 10 months after the genetic sequence of a variant is known, Bright said. And relying on eggs presents an additional risk when it comes to bird flu because a pandemic could wipe out billions of chickens, crashing egg supplies. ????? ???????  

Time matters because flu viruses mutate constantly, and vaccines work better when they match whatever variant is circulating. ????????????

Researchers can make bird flu vaccines in other ways, but mRNA vaccines are developed much more quickly because they don't rely on finicky biological processes, such as growing elements of vaccines in chicken eggs or cells kept alive in laboratory tanks. ?????  

As hundreds of herds and dozens of people were infected in the U.S., the Biden administration funded Moderna to develop bird flu vaccines using mRNA technology. As part of the agreement, the U.S. government stipulated it could purchase doses in advance of a pandemic. That no longer stands. ????? ???????  

The most pertinent pandemic threat today is the bird flu virus H5N1. Researchers around the world were alarmed when it began spreading among cattle in the U.S. last year. Cows are closer to humans biologically than birds, indicating that the virus had evolved to thrive in cells like our own. ????????????