Toxoid vaccinesToxoid vaccineA vaccine made from a toxin (poison) that has been made harmless but that elicits an immune response against the toxin. are based on the toxin produced by certain bacteria (e.g. tetanus or diphtheria).
The toxin invades the bloodstream and is largely responsible for the symptoms of the disease. The protein-based toxin is rendered harmless (toxoidToxoidInactivated or killed toxin (poison) used in vaccine production.) and used as the antigen in the vaccine to elicit immunity.
To increase the immune response, the toxoid is adsorbed to aluminium or calcium salts, which serve as adjuvants.
Safety and stability
Toxoid vaccines are safe because they cannot cause the disease they prevent and there is no possibility of reversion to virulence. The vaccine antigens are not actively multiplying and do not spread to unimmunized individuals. They are stable, as they are less susceptible to changes in temperature, humidity and light.76