A Pfizer Drug Could Potentially Prevent Alzheimer's. They Decided Not to Test It.

The Pfizer company logo is photographed at Pfizer Inc. headquarters, in New York, Monday, Dec. 4, 2017.

Pfizer's arthritis drug appeared to reduce the risk of getting Alzheimer's disease.Christopher Rowland, business reporter focused on the health-care economy's effects on patient health, costs, and privacy for The Washington Post, explains why they kept it a secret.