From Jonathan Cohn's New Republic article, Creative Destruction:

The single biggest source of medical research funding, not just in the United States but in the entire world, is the National Institutes of Health (NIH): Last year, it spent more than $28 billion on research, accounting for about one-third of the total dollars spent on medical research and development in this country (and half the money spent at universities). The majority of that money pays for the kind of basic research that might someday unlock cures for killer diseases like Alzheimer's, aids, and cancer. No other country has an institution that matches the NIH in scale. And that is probably the primary explanation for why so many of the intellectual breakthroughs in medical science happen here.

There's no reason why this has to change under universal health insurance. NIH has its own independent funding stream. And, during the late 1990s, thanks to bipartisan agreement between President Clinton and the Republican Congress, its funding actually increased substantially--giving a tremendous boost to research. With or without universal coverage, subsequent presidents and Congress could ramp up funding again--although, if they did so, they would be breaking with the present course. It so happens that, starting in 2003, President Bush and his congressional allies let NIH funding stagnate, even though the cost of medical research (like the cost of medicine overall) was increasing faster than inflation. The reason? They needed room in the budget for other priorities, like tax cuts for the wealthy. In this sense, the greatest threat to future medical breakthroughs may not be universal health care but the people who are trying so hard to fight it.

via - Paul Krugman