Vaccines aren't natural.
Look at from an outsiders' perspective. As if you're a member of an alien species monitoring life on earth throughout it's entire history. The humans are just the animal that for now has ended up at the top of the food chain. Now they've developed the steam engine, completely natural, just those humans developing and socially evolving. Oh wow look those humans can alter genetics. Took us double the time to do that. Now they can digitalise their brains. Uh-oh, they didn't colonise another planet before the ice age hit. Wow, radical climate change and they all died. Oh wow look small mammals survived. See, just another animal that's evolving, nothing unnatural bout our scientific advancements.