Only point of contention with this (because otherwise you've said everything i could possibly say) is this:

Everyone is terrified of these aliens, who the last time they were on Earth, didn’t really threaten much, instead, they offered a vaccine in trade, a vaccine that healed millions…

I could be wrong, and I'm at work, so I can't rewatch that episode, but the impression I gathered was that the aliens were the ones that had sent the virus in the first place, and the numbers that it would kill were pretty staggering. Maybe not overtly scary, but it would give me shivers knowing that they managed to infect however many people unknowingly. They way you have it worded (to me at least) is that they just happened to have the vaccine to bargin with, instead of holding so-and-so amount of people hostage.

Otherwise I think you have the best CoE reaction that I've read yet! I've actually put off reading your other stories (Bred in the Bone and Fallout ..new part, yay!... to read through this whole post, and comments!