The flu vaccine has been available for four decades and yet the death rate from the flu remains high. Why?
D000367:Age Factors; D000368:Aged; D006801:Humans; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000600:supply & distribution*; D007251:Influenza, Human / Q000401:mortality* / Q000517:prevention & control
D007252:Influenza Vaccines