But the whole-cell pertussis vaccine isn't coming back to the U.S., Witt says. U.S. companies no longer make it and if they were to start again, they would have to get approval from the Food and Drug Administration just as if they were introducing a whole new drug. That's probably not worth the risk. Instead, companies are more likely to work on a better, longer-lasting vaccine that doesn't have those whole-cell side effects. "It's probably the better solution," Witt says.