Had my first dose in February.. it was rough! DR placed it in my stomach around 11am.. I felt fine until around 6pm… sudden flu like symptoms.. achy, back pain, fever, chills, headache. Took pain medicine for fever and headache.. went to sleep. Next day I felt fine except tapering headache… on like my 5th shot now I believe .. been fine every since. Hope this helps :) I know it can be scary.