i had understood that what enabled generics to be made was that IP rights had expired? 15 years IIRC.Far as I can see the letter is basically making a false equivalency between generic drugs and vaccine manufacturing.
The generic drugs necessarily have slightly different formula/makeup for the very reason that big pharma won't let go of the IP rights, so 'generic' manufacturers are forced to make something that might have a different level of effectiveness but doesn't involve just giving all the money that buys them to one pharma giant.