Flu shots also use a vaccine mechanism that's been known/used for decades and is not a first of its kind in history mRNA treatment. I feel like this difference would lead towards one requiring more testing than the other, at least in a rational society.
[Edit] For anyone that wants to downvote this, please explain what I said that was untrue. Flu shots in the US have never been mRNA based. Covid shots in the US are mRNA based. Before covid, there was never at any point in history an mRNA based vaccine rolled out to the public.
[Edit] For anyone that wants to downvote this, please explain what I said that was untrue. Flu shots in the US have never been mRNA based. Covid shots in the US are mRNA based. Before covid, there was never at any point in history an mRNA based vaccine rolled out to the public.