Does tetanus toxoid contain horse serum?

Tetanus toxoid has never contained horse serum or protein. Equine tetanus antitoxin (horse derived) was the only product available for the prevention of tetanus prior to the development of tetanus toxoid in the 1940s. Equine antitoxin was also used for passive post-exposure prophylaxis of tetanus (e.g., after a tetanus-prone wound) until the development of human tetanus immune globulin in the late 1950s. Equine tetanus antitoxin has not been available in the U.S. for at least 40 years.