U.S. pharmacy chains are preparing a big push for flu vaccinations when the season kicks off in October, hoping to curb tens of thousands of serious cases that could coincide with a second wave of coronavirus infections. CVS Health Corp, one of the largest U.S. pharmacies, said it is working to ensure it has vaccine doses available for an anticipated surge in customers seeking shots to protect against seasonal influenza. Rival chain Rite Aid Corp has ordered 40 percent more vaccine doses to meet the expected demand. Walmart Inc and Walgreens Boots Alliance said they also are expecting more Americans to seek these shots.