Where my DH and I work we both frequently use needles and see blood. When people first start working at either place they do sometimes have difficulty and we help them with a stepwise approach to desensitize. First they take syringes out of the package and practice drawing up water, then putting on the needle, then injecting an orange, then injecting the real thing. All the steps up to the last one are practiced as many times as they want. We also avoid social reinforcement of their fears, so that means not supporting or enabling the avoidance of the feared item (blood, syringe, or needle). I do tell them a reaction is normal and that many people don't like these things, but that most people desensitize over time. Even though people have previously experienced vaso-vagal symptoms, we don't dwell on that aspect and, so far, this approach works well.
At home with DD, we emphasized that there is a need for the procedure and answered each question honestly. "Will this hurt?" "Yes, a little just while it's happening (or for a little while after for vaccinations)". We talk about coping skills like thinking about something really interesting, talking to the parent who is with you, sing a song in your head, etc. When DD was small, we gave her the choice of holding still herself, or being held down. She found this empowering and was able to hold still by herself starting at about age 3 (much to the shock of the nurse giving the shot! LOL!). This was a great relief to me, because I really hated holding her down!
