Hi, Well from what I can tell you do suffer from vasovagal syncope. The vasovagal syncope trigger causes a sudden drop in your heart rate and blood pressure. That leads to reduced blood flow to your brain, which results in fainting. It is a harmless condition and doesnt require any kind of treatment A flu shot isnt something you require to continue your daily life, so you can skip it. Its not an issue. But if you really do want to have the shot, I recommend lying down before hand and having your legs raised, this will help increase the blood flow to your brain and help in preventing you from fainting. I hope this answered your question.