This summer program looks like a great deal! All expenses paid and you may be able to get course credit for this. Anyone from first-year students through recent graduates can apply (you have to be a US citizen or permanent resident), but it is competitive because groups are small. Looking at the application for the BU program, it looks like it might give you a competitive edge if you had some math or computer science background–but that’s not a prereq for applying.
Programs at the different institutions differ in their start dates, area of emphasis (epidemiology, medical genetics, etc.), and application forms. The deadlines for applying are a month or so away, but they’re already considering applications, so apply soon! Take a look at the general flier (link below) and a few of the programs at the various institutions (urls are on the flier), and if it looks to be of interest, go for it! Click for details.