It's quite simply really, the vaccines are known to carry a risk of harm, but this risk is considered insignificant just as any one person not really important in the face of "progress". The casualties of vaccines and all other forms of bad medicine are drowned out by the "good" that vaccines do us all. Taking a vaccine in many cases, like the flu vaccine for instance, is like "taking one for the team". It's down right heroic!
A friend at work bragged the other day that he got a coupon from Target just for taking a free vaccine...... this should tell you something. You get what you pay for my friends..... they are paying us to take vaccines we don't need.