I'd say your chances are better at a bio/pharma strategy consulting specialist or one that at least does a good bit of that type of work (LEK Boston office comes to mind). At a top 3 (MBB) firm, you will NOT be working exclusively or even mainly on healthcare cases. Best you can do is go for a strong healthcare office (usually Boston) that does a good amount of pharma work and has maybe 20-30% tops of caseload in health care. So you'll get more than you would at another office, but everyone out of undergrad is hired as a generalist at the top 3 strat firms.
Caveat: You do get to specify your preferences and efforts will be made to accomodate them, but staffing is mainly a function of who's available firm-wide when a project is starting rather than managed within an individual industry practice. This is all at the most junior level (coming out of ugrad), higher ups definitely get more specialized and work in a specific industry but the firm needs a general pool of people that can be thrown at any case.