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[Pharmacology](https://durgical.com/en/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

## Key points

- Toxoid = inactivated toxin that still induces antibodies: the basis of tetanus and diphtheria vaccines.
- Plain polysaccharide → T-independent response, poor under two years of age and with no booster effect; conjugation to a carrier protein fixes this.
- Surviving tetanus or diphtheria does not leave reliable immunity: survivors also need vaccination.
- BCG is a live vaccine: it is not given to immunosuppressed people or during pregnancy.
- Conjugate vaccines also protect the unvaccinated because they reduce carriage and transmission (herd effect).

## 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](https://durgical.com/en/pharmacology/bcg-vaccine/)
- [**Diphtheria vaccine (diphtheria toxoid)** Inactivated diphtheria toxin that induces antitoxin antibodies. It is almost always combined with tetanus and… Immune response against diphtheria toxin](https://durgical.com/en/pharmacology/diphtheria-vaccine/)
- [**Haemophilus influenzae type b (Hib) vaccine** Conjugate vaccine: Hib capsular polysaccharide linked to a protein. It nearly eliminated Hib meningitis and… Immune response against the Hib capsule (polyribosyl-ribitol-phosphate, PRP)](https://durgical.com/en/pharmacology/haemophilus-influenzae-type-b-vaccine/)
- [**Pertussis vaccine** Whole-cell or acellular vaccine (purified components such as pertussis toxin) that protects infants from severe… Immune response against Bordetella pertussis and its toxin](https://durgical.com/en/pharmacology/pertussis-vaccine/)
- [**Pneumococcal vaccine** Conjugate (for infants and adults) or polysaccharide vaccines against the pneumococcal serotypes that most often cause… Immune response against the Streptococcus pneumoniae capsule](https://durgical.com/en/pharmacology/pneumococcal-vaccine/)
- [**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)](https://durgical.com/en/pharmacology/tetanus-vaccine/)
- [**Meningococcal vaccine** Conjugate vaccines against serogroups A, C, W and Y, and protein vaccines against B. They prevent meningococcal… Immune response against Neisseria meningitidis](https://durgical.com/en/pharmacology/meningococcal-vaccine/)

## 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.

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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](https://list.essentialmeds.org/) (World Health Organization, 2025); [Meningitis](https://www.who.int/news-room/fact-sheets/detail/meningitis) (World Health Organization, 2026); [Chapter 8: Haemophilus influenzae | Pink Book | CDC](https://www.cdc.gov/pinkbook/hcp/table-of-contents/chapter-8-haemophilus-influenzae.html) (Centers for Disease Control and Prevention, 2021); [Chapter 21: Tetanus | Pink Book | CDC](https://www.cdc.gov/pinkbook/hcp/table-of-contents/chapter-21-tetanus.html) (Centers for Disease Control and Prevention, 2021).

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