I've not researched this link thoroughly, but I do remember reading about it, and there is a legitimate link. I know that Dr. Sears mentions it somewhere. I actually remember reading that there is a correlation between delaying beginning vaccinations at four months old instead of two months and a reduced risk of asthma (statistically significant reduced risk).
My dd received her two month vaxes (all of them), and based on her reaction and my subsequent researching, I am now a fully non-vaxing mama. So far, no asthma or any long-term consequences. She's now 2.