This year's influenza strain has been spreading quickly throughout the country, sparking outbreaks in a number of regions, including Colorado, where 4,000 cases have been confirmed and three children have died from the disease. The Centers for Disease Control and Prevention says that the flu has been reported by 39 states already this year, lending credence to officials' suggestions that this could be one of the more dangerous flu seasons in recent memory--especially since doctors in Colorado are reporting a very severe virus. Though this year's flu vaccine does not contain the exact flu strain subtype that is suspected of infecting most people in the United States, the vaccine will provide some protection against the flu despite the differences. Even when matched perfectly with the strain that has erupted in a given year, the vaccine is not 100 percent effective; only 70 percent to 90 percent of healthy adults under the age of 65 years are protected in an ideal vaccine situation.