Great job.
This is a one heck of a cool game. It's easy to pick up, and very addictive once you get the hang of it. I love the super attack bar - simple, but still well designed and worth thinking about. I like how the enemies are varied in look and attack, and the final boss is really cool. The graphics are tight, and as a biology/chemistry sort of person, I can appreciate the whole vaccine/viruses theme.
The only things I would change would be to make the game a good bit longer (although I'll take a little of a good thing over a lot of crap any day), and maybe somewhat harder - it's a little too easy to just sit back, swallow a few enemy bullets, and then shoot with the freedom to know you can clear everyone out with the charged super attack if necessary. Still, great game!