In addition to what Rapaire said, the influenza vaccine contains inactivated strains of virus. If it were possible for anything to get into the culture when the vaccine was growing in the egg medium, it would be inactivated by the same process.

I think the chance of a pandemic is quite slim.
I also think the chance of the mother of all hurricaines causing the damage it did in New Orleans, I think the chance of the unjustifiable death and suffering due to lack of government action is slim. I think 20 - 100 MILLION of the world's citizens dying from flu in one single outbreak are slim. All of these things happened.

When I worked in public health, sometimes what we did was try to head off panic and sometimes it was simply trying to get folks to take threats seriously. People get hysterical, or they resent having to think about possible disasters and ridicule anybody who does, whether the people they're making fun of are over-reacting or just making sure they have batteries and a full pantry. I think the smartest thing to do is just develop an appropriate plan, get prepared, and then go on with life as usual.