Ideally they should be cats trained by their mothers in the art of hunting. Which is why actual barn cats are generally better.
My friend's cat, who is a few years old but does not look full grown, killed a rat in their house. They were both immensely grossed out and proud. Then they had to figure out how to get rat blood out of their carpets.
I had the flu shot in November. Work always does a clinic for employees. However the cold I had around Christmas was v. flu-like, lots of aches and exhaustion.