Need To Know News 18-12-18 Original post Cached copy Over 40% of Americans Now Refuse Flu Vaccines as Awareness of Side Effects Spreads Need To Know News - 2018-12-18 - Original post - Cached copy The top three reasons include harmful side effects, fear of getting the flu from the shots, and conviction that the shots don't work anyway. Those under the age of 45 are the most likely to reject vaccines.