Streptococcus equi equi, the causative organism of equine strangles, is a highly contagious bacteria first described as an equine pathogen in 1251 by Jordannus Rufus. Though veterinary medicine has been faced with the challenges of infection with Streptococcus equi equi for several hundred years, there has been limited progress in developing a safe and efficacious vaccine. In 1998 a modified live intranasal vaccine, Pinnacle IN, was developed based on genetic deletion of the hyaluronic acid capsule; a known virulence factor of Streptococcus equi equi. Since its introduction there have been several reports of post-vaccinal reactions, including abscesses, purpura hemorrhagica, and clinical signs of disease. This seminar reviews pertinent information concerning Streptococcus equi equi, explores posssible theories of post-vaccinal reactions due to intranasal strangles vaccination, outlines the most common types of vaccinal reactions and discusses methods for decreasing the likelihood of reactions when utilizing intranasal strangles vaccination.