Public health officials have found that influenza vaccination rates among adults dropped in recent years, leading some experts to conclude that was likely a contributing factor to making the 2017-18 season the deadliest flu outbreak in recent memory.Recent reports from the national Centers for Disease Control and Prevention offer more details on the past flu season, which hospitalized or killed more Americans than any seasonal flu in more than 40 years.The federal health protection agency estimated the United States had a 37.1 percent influenza vaccination coverage during the 2017-18 season, a 6 percent decrease from the previous season, according to the latest reports.