With all the talk about the flu vaccine shortage, ever wonder how the vaccine is made? It's made from virus that's grown in chicken eggs. And health officials concede the vaccine can't just be cranked out when needed on short notice. For example, it could take six months if a new vaccine had to be made in a hurry to fight a super-strain flu pandemic. Flu vaccine is also the only vaccine made fresh every year, and it's a matter of delicate timing, as experts decide which strains to fight, in time to get a vaccine out. The Associated Press was granted a rare look inside the factory of Aventis Pasteur, America's only flu shot maker. There are about 15-hundred workers at the gated, 50-building, 70-acre compound that's a two-hour drive north of Philadelphia. Like many Americans, the workers there won't be getting the benefit of their product. The company has told them to forego the shots unless they're at high risk.