Figure 3. Antiviral drug access in underinsured populations for single-chain and 2-chain pharmacy distribution networks during the 2009 influenza pandemic, Texas, USA. Each network contains a maximum of 723 distribution points, and was designed by using a hybrid optimization that maximizes coverage in small ZIP code (US postal code) areas and overall (see text for details). Color indicates the expected percentage of the underinsured population willing to travel to dispensing pharmacies to obtain antiviral drugs A) statewide and B) in small ZIP code areas. Numbers along the baselines and the y-axes indicate single-chain networks. 1, Walgreens; 2, CVS; 3, Walmart; 4, HEB; 5, Kroger; 6, Target; 7, Brookshire; 8, Sam’s Club; 9, Tom Thumb; 10, Randalls; 11, United; 12, Costco; 13, Kmart; 14, Independents (independent pharmacies).