One consideration with the mass use of flu vaccine in healthy children is the removal of natural antibodies to flu which are obtained from natural infection. (wellnessmama.com)
They help to increase natural antibody levels and white cell activity in dogs, as well as control and raise hormone levels. (dogfoodselector.com)
Since so few dogs had developed natural antibodies in the late 1970's, a large number of dogs died from this disease. (lbah.com)