HIB was the first shot we gave DS, and I agree with the pp who said that menigitis is scary. My brother had spinal meningitis (no clue what type) when he was about 11, and I remember the spinal tap and everything with him in the hospital for a few weeks and it was just a very scary time. Not something I'd like to repeat from a parenting perspective.
That said, I'm not a big fan of vaccinations overall, and we didn't do the prevnar (isn't that a combined shot?). I just looked up the prevnar vaccine, and interestingly, it also talks about meningitis on the product site from Wyeth. Perhaps that is the link between the two vaccines?
I don't know. We didn't do the prevnar, just the HIB vaccine, and we've not yet done polio. My MIL really wants us to do that one, but I think that it's a mostly moot point these days.