For years, the world's vaccine companies have labored in the shadows of the pharmaceutical industry, vilified by parent groups who claim childhood vaccines can cause neurological disorders like autism. Now, almost overnight, these same companies have been thrust to the forefront of a massive campaign to produce a vaccine against pandemic flu. Not since Jonas Salk's work to find a cure for polio in the 1950s have vaccine scientists been so squarely in the vanguard of medicine. The challenges are vast. The unanswered questions surrounding the influenza virus are profoundly difficult, the process for producing vaccines is slow and unwieldy,...