Recommended shots for traveling vary a lot by destination. I imagine that Iceland wouldn't require anything more than when I went to Denmark, and that only required shots you should already have had. (They suggested also getting a hepatitis shot, but I declined.)

months, ideally. But I doubt iceland would have any vaccines. The tropics is where the nasty diseases is at.

I will go by the BBC's article a couple years back.
http://news.bbc.co.uk/1/hi/health/4311613.stm

I don't think there is one. But I do think that vaccines sometimes cause fatal autoimmune reactions, and that the chance is higher: the younger the child, the more vaccines given at once, and for certain "bad lots" of produced vaccines. But I've only known one adult who had a bad reaction to one.