Toxoid vaccines

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

Adverse reactions associated with toxoid vaccines

	Vaccine	Rare, more severe adverse reactions	Comment
	Tetanus toxoid (TT)⁶⁸	Anaphylaxis AnaphylaxisAn acute, multi-system, allergic reaction (IgE mediated) to a substance, such as vaccination, drugs, and food. Symptoms of anaphylaxis may include breathing difficulties, loss of consciousness, and a drop in blood pressure. This condition can be fatal and requires immediate medical attention. (1.6 per million doses) and brachial neuritisBrachial neuritis (also known as brachial plexus neuropathy or neuralgic amyotrophy) A neuropathy that presents as a deep, steady, often severe aching pain in the shoulder and upper arm and may include muscular weakness. (0.69 cases per 10 million) are extremely rare.	LocalLocal (or localized)Restricted or limited to a specific body part or region. and systemicSystemicRelating to a system, or affecting the entire body or an entire organism (e.g., fever). reactions increase with increasing number of doses.
	Diphtheria toxoid (DT and Td)⁶⁹	Temperature in excess of 40.5 °C (0.3%), febrile seizures (8 per 100,000 doses) or hypotonic–hyporesponsive episodes (0 – 291 per 100,000 doses).	No anaphylactic reactions attributable to the diphtheria component have been described.

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