I have heard that flu shots generally are manufactured in eggs or chicken embryos, and so there can be an issue for people who are allergic to eggs. What other shots should people allergic to eggs know could set off their allergies?
I am not sure where you "heard", but currently people with egg allergy are merely asked to stay for observation 30 mins after a flu shot, but a reaction is not expected due to the very small volume. The only one I know that is a total no is yellow fever. Here is additional info on egg allergy & vaccinations. http://www.chop.edu/centers-programs/vaccine-education-center/vaccine-ingredients/egg-products