Definition
Toxoids are inactivated bacterial toxins that retain antigenicity but lack toxicity.
They are used to immunize against toxin-mediated diseases.
General Method of Preparation
1) Selection and Growth of Toxin-Producing Bacteria
The bacteria are cultured in a medium that promotes toxin production.
Example: Corynebacterium diphtheriae for diphtheria toxoid.
2) Toxin Extraction and Inactivation
The bacterial toxins are harvested and purified.
They are inactivated using formalin (0.3%-0.5%) at 37°C for 1-4 weeks.
3) Adjuvant Addition
Commonly combined with aluminum hydroxide to enhance immune response.
4) Sterile Packaging and Storage
Stored at 2–8°C for stability.
Examples of Toxoids
Diphtheria Toxoid – Used in DTaP vaccine
Tetanus Toxoid – Used in TT and DTaP vaccines
