The discovery of protease inhibitors, and the popularization of highly-active antiretroviral therapy (HAART, or the "AIDS cocktail") would definitely fall into this category. It goes without saying that AIDS was (and is) a massive public heath issue. However the advent of protease inhibitors and HAART dramatically changed AIDS from "a death sentence" to a "chronic, manageable condition" (terminology I find somewhat problematic, but are still in use.) This really transformed the landscape of AIDS in the US (and in other countries, although in slightly different ways.) The first protease inhibitor was approved in 1995; by 1996, AIDS deaths had dropped off dramatically. People often joked about protease inhibitors having a "Lazarus Effect," in the sense that they often brought people back from the brink of death. So in that sense, it had an impact not dissimilar from the Polio vaccine, in terms of scope and impact. Although, of course, HAART is not a vaccine but merely a treatment, albeit one that has been incredibly impactful and important.

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