The “Gateway to the West” — home to some of the country's most influential vaccine research and development institutes, including the Washington University School of Medicine — may be quickly losing its ability to prevent infectious diseases. The story of St. Louis is emblematic of the nation’s immunization declines. A combination of rising exemptions, difficulties accessing health care services, and anti-vaccine messages fueled by social media and, more recently, the federal government, has laid a path for preventable diseases to explode in the U.S. The vast majority of counties across the United States are experiencing declining rates of vaccination and have been for years, according to an NBC News investigation, the most comprehensive analysis of vaccinations and school exemptions to date. In 2010, almost 90% of kindergartners attending school within the St. Louis city limits had their recommended measles-mumps-rubella (MMR) shots, which prevent nearly all cases of measles – th...