Thirty-eight million people around the globe are infected with HIV, and 8,000 of them die each day from AIDS. Although anti-HIV drugs can extend lives, they have serious limitations, and the vast majority of infected people still do not have access to them. So it is hard to overstate the need for an AIDS vaccine that c an slow the virus's spread and ultimately safeguard the world's population.

Scientists in academia, government, and the pharmaceutical industry have spent the last 18 years testing three dozen different AIDS vaccines in human studies. Time and again, high hopes have given way to crushing disappointments, and the field has been roiled repeatedly by bitter disputes about the best way to move forward. If the different players worked in isolation, as private companies often do, the tensions might not matter much. But in the world of international vaccine research, there's a constant tussle for resources and influence among government agencies, universities, drug companies, health ministries, networks of clinics, and the communities that agree to participate.