Sanofi has joined the race to combat coronavirus as the outbreak is kindling fears of a pandemic. The question is whether its effort will prove more effective than some of Big Pharma's past attempts to tackle dangerous new pathogens.

The French drugmaker said Tuesday it will team up with a U.S. agency to develop a vaccine against the virus that has killed more than 1,800 people. Sanofi is betting its earlier work to develop a SARS vaccine will speed the effort.

Every new health crisis poses a similar dilemma: Pharmaceutical companies must respond with swift solutions in a context where the science, the outlook and the potential payoff are murky at best. Developing a vaccine typically takes years. By the time they're ready, the crisis has often abated, leaving little incentive to carry on with the work.