The flu

Formaldehyde is a natural byproduct of the body.  It's used in a really small amount as a preservative in vaccines.  Far less than what your body produces on its own.  Because it produces this itself, it can also get rid of it as well. 

Aluminum is toxic at MUCH higher concentrations than what's in vaccines.  Because it's so abundant on our planet, we're consuming a good bit of it just in everyday life.  Much more than is in vaccines.  It's in vaccines, so our bodies react more strongly to it to help increase immunity. More antibodies are produced.  It's sounds scary, but put into context, it's really not that bad. 

Now if you just don't want the vaccine, that's fine. 

Yeah, the stuff sounds scary, but there's a reason it's in there and they're doing a lot of research to make sure that it's safe. 

I got the flu once when I was little (I'm talking elementary school when everyone likes to send their sick kids to school). That was it. I didn't get the swine flu shot and didn't get not one sniffle that year. I rarely get sick. Thank you great immune system!