How are toxoid vaccines made from bacterial toxins?

Toxoid vaccines are created by neutralizing the harmful effects of bacterial toxins while preserving their ability to stimulate an immune response. In many bacterial diseases, the primary danger arises from exotoxins produced by the bacteria rather than the bacteria themselves.

To produce a toxoid, scientists treat these bacterial toxins with heat or specific chemicals, most commonly formaldehyde. When toxins are incubated with formaldehyde at 37 °C (98.6 °F) for several weeks, the toxin is rendered harmless without altering its structure as an immunogen.12

Once this modified, inactive toxin is injected into the body, it acts as an antigen, prompting the immune system to produce antibodies. These antibodies are capable of recognizing and neutralizing the active toxin if the body is exposed to it later, thereby conferring immunity. To further enhance this response, toxoids are often adsorbed onto an inorganic gel, which helps ensure the vaccine is retained by macrophages for a more effective, long-lasting immune reaction.12