That's a tough one. Perhaps a topic for an ethical debate.
I am one to say 'what's done is done', I can't change the past... ie. I can't change that animals were tested on and that there are now vaccines available.
So next question, do I take the vaccine.
I don't want to hurt animals. People are animals too so I don't want to hurt people. Is there greater harm done by taking the vaccine or not taking it? If the vaccine is for a particularly lethal contagious disease I think it might be a good idea to take it. But flu vaccine... no, that vaccine is more to protect the individual. Usually only the weak succumb to the flu (children, sick and elderly). I haven't had a cold (or a sick day from work) even since becoming vegan, so I think healthy eating must have some protective quality.. (just my opinion so far, I could change that opinion in time... we'll see). Regardless... I don't feel a flu shot is necessary for most people.
If you work in hospitals, I think you would be obligated to have all shots.. to protect yourself as well as the patients since you will be coming into contact with all sorts of viruses and bacteria.
Have you hear of the book 'Bird Flu.. a Virus of Our Own Hatching'
? The author of that book predicts the inevitability of a massive worldwide pandemic which will basically be caused by conditions of factory farming (overcrowded, filthy and antibiotic laden) - ie. factory farms are providing a breeding ground to create the perfect storm.