The following excerpt is from an article that originally appeared on Doom and Bloom
Why Are Flu Vaccines Sometimes Ineffective?
The Centers for Disease Control and Prevention (CDC) are reporting that 36 states are in the midst of widespread influenza outbreaks. It appears that this flu season might be a bad one, but why? And will the usual vaccines be effective in preventing you for getting the flu this winter?
You might think that, okay, I got the vaccine, so I can’t get the flu this winter. You might be surprised to know, however, that the CDC shoots for about 40-60% vaccine effectiveness in preventing the illness, not the 100% you expected. In fact, last year’s vaccine was 42% successful (less against H3N2), on the low end of the CDC’s target, but in 2014-2015, the prevention rate from the flu vaccine was about 19%.
(Note: This is neither an anti-vaccine nor pro-vaccine article. It is simply a discussion as to whypost was originally published on this site