Catherine,

As the (unwilling!) coordinator of our hospital's flu shot campaign, I have
before me the CDC (Center for Disease Control) Recommendations and Reports on
who should or should not receive flu vaccine.  It recommends that women who
will be postpartum or in the 3rd trimester of pregnancy during flu season
receive the vaccine.  Since the vaccine uses dead virus to stimulate the
person's immune system to develop antibodies, it is impossible to contract or
spread influenza from having the vaccine.

Since the elderly and children are at most risk from flu, it would actually
benefit her breastfeeding baby if she has the vaccine.

Hope this helps!

Carol, St. Louis, MO