hey /a/, I need help, no one else could help me, this board is my last chance.

I remember a movie from my childhood, it was about spaceship that had to be shrank and injected into some person (princess or someone important) to fight against some virus (maybe) to save her.
it was animated and I'm 80% sure it was japanese. even if it was some other country it sure was anime style.

I saw it around 15 years ago on VHS so it sure was something old.

any hints please?
I just have this urge to see it but I can't find it anywhere...