They changed the definition because the technology changed. The word 'trolley' used to mean cart but it doesn't any more because the technology changed. mRNA technology is over 50 years old but it only recently has been applied to vaccines, so that definition had to be changed.
They changed the definition because the technology changed. The word 'trolley' used to mean cart but it doesn't any more because the technology changed. mRNA technology is over 50 years old but it only recently has been applied to vaccines, so that definition had to be changed.
Get a grip.