Pharmacology · Class
Bacterial and antimalarial vaccines !
Vaccines against bacteria and their toxins (tetanus, diphtheria, pertussis, Hib, pneumococcus, meningococcus, tuberculosis) and against malaria.
Updated 2026-11-01
What they are
Products that teach the immune system to recognise a bacterium, its capsule or its toxin before real contact. They include toxoids (inactivated toxins), plain capsular polysaccharide vaccines, conjugate vaccines, purified-component vaccines and live attenuated vaccines such as BCG. Combination vaccines (DTP, pentavalent, hexavalent) are described on each component's page.
Mechanism of action
They produce active immunity: antigen-presenting cells take up the antigen, helper T cells and B cells are activated, and antibodies and memory cells remain. Toxoids raise antibodies that neutralise the toxin. Plain polysaccharides are T-independent antigens and work poorly in infants; linking them to a carrier protein (conjugation) makes them T-dependent, with memory and boosting.
Target: Adaptive immune system (B and T cells) against bacterial antigens or toxins
Drugs in this class
- BCG vaccine (bacille Calmette-Guérin)Live attenuated tuberculosis vaccine. It protects children from severe forms, such as tuberculous meningitis and…Cell-mediated immunity against Mycobacterium tuberculosis
- Diphtheria vaccine (diphtheria toxoid)Inactivated diphtheria toxin that induces antitoxin antibodies. It is almost always combined with tetanus and…Immune response against diphtheria toxin
- Haemophilus influenzae type b (Hib) vaccineConjugate vaccine: Hib capsular polysaccharide linked to a protein. It nearly eliminated Hib meningitis and…Immune response against the Hib capsule (polyribosyl-ribitol-phosphate, PRP)
- Pertussis vaccineWhole-cell or acellular vaccine (purified components such as pertussis toxin) that protects infants from severe…Immune response against Bordetella pertussis and its toxin
- Pneumococcal vaccineConjugate (for infants and adults) or polysaccharide vaccines against the pneumococcal serotypes that most often cause…Immune response against the Streptococcus pneumoniae capsule
- Tetanus vaccine (tetanus toxoid)Inactivated tetanus toxin that induces protective antibodies. It prevents tetanus, including neonatal tetanus, and is…Immune response against tetanospasmin (tetanus toxin)
- Meningococcal vaccineConjugate vaccines against serogroups A, C, W and Y, and protein vaccines against B. They prevent meningococcal…Immune response against Neisseria meningitidis
Others in the class
- Cholera vaccine
- Typhoid vaccine
- Malaria vaccine
Test yourself
Think of the answer, then tap the question to see it.
Why does a plain polysaccharide vaccine protect an infant poorly?
Polysaccharide is a T-independent antigen: it activates B cells without T-cell help, and under two years of age that response is weak and leaves no memory.
What changes when a polysaccharide is conjugated to a carrier protein?
It becomes T-dependent: helper T cells assist B cells, memory forms and repeat doses boost the response, even in infants.
What is a toxoid?
A bacterial toxin that has been inactivated so it no longer causes harm but keeps its epitopes, so it induces neutralising antibodies against the real toxin.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: eEML - Electronic Essential Medicines List (World Health Organization, 2025); Meningitis (World Health Organization, 2026); Chapter 8: Haemophilus influenzae | Pink Book | CDC (Centers for Disease Control and Prevention, 2021); Chapter 21: Tetanus | Pink Book | CDC (Centers for Disease Control and Prevention, 2021).
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Representative model, for educational purposes only.