E. coli scours is notorious and E. coli scours protection has been problematic. As mentioned above, E. coli bacteria produce powerful endotoxins that can damage tissue both locally and systemically, and their cell wall contains damaging endotoxins. It is difficult to remove this endotoxin from whole E. coli cells in the vaccine manufacturing process. So, E. coli products have a reputation for being highly reactive, causing significant injection site lumps and bumps, and even more serious reactions such as abortion.

Because of these E. coli vaccine problems, Schering-Plough Animal Health scientists concentrated on developing a product that was more effective and less reactive. They utilized new—sub-unit—production technology specifically designed to enhance a specific immune response without significant side effects. With this technology, whole E. coli cells are not part of the vaccine. The vaccine is manufactured only with sub-units of the bacteria: the K99 surface antigens that stimulate immunity. These are what the immune system recognizes and responds to. So, with Guardian®, a highly specific and safe immune response occurs, without the degree of risk associated with whole cell vaccine technology.

The result is that Guardian vaccination is smooth, and injection site and systemic reactions are minimized. The table below compares the K99 E. coli components of Guardian, ScourGuard, and Scour Bos 9.

Only Guardian utilizes the newer sub-unit E. coli technology. Scour Bos 9, with four whole-cell strains of E. coli, offers broad E. coli protection, but it is not a good trade-off for the safety of a sub-unit compared to a whole-cell product. Of the three major scours vaccines on the market, Scour Bos 9 may be the most reactive.