My understanding is that it's not regulations that stops american pharmaceutical companies from making this vaccine, it's the profit margin. It's more financially rewarding to make drugs rather than vaccines, particularly as manufacturing the flu vaccine is such a "compressed" venture (i.e. a large quantity of vaccine to be made in the short period of time from when the CDC decides which strains need to go into the vaccine, to the time of delivery). I saw something very funny in the newspaper this morning: the editorial was complaining about British government having the power to control the U.S. vaccine supply, but failing to acknowledge that it was better to impound contaminated vaccine than let it be supplied!