Classification of vaccines

Vaccines can be classified into several categories based on their composition and the method by which they are produced. Here are the main types of vaccines with examples:

 

1. Live-Attenuated Vaccines

• Definition: These vaccines use a weakened form of the pathogen (virus or bacteria) that can still replicate but doesn’t cause illness in healthy individuals.
• Examples:
  • Measles, Mumps, and Rubella (MMR) vaccine
  • Varicella (chickenpox) vaccine
  • Oral Polio Vaccine (OPV)
  • Yellow Fever vaccine

2. Inactivated (Killed) Vaccines

• Definition: These vaccines contain pathogens that have been killed or inactivated so that they cannot replicate, but can still elicit an immune response.
• Examples:
  • Inactivated Polio Vaccine (IPV)
  • Hepatitis A vaccine
  • Rabies vaccine
  • Influenza (inactivated) vaccine

3. Subunit, Recombinant, Polysaccharide, and Conjugate Vaccines

• Definition: These vaccines use specific parts of the pathogen (like proteins or polysaccharides) to elicit an immune response. Conjugate vaccines link antigens to carrier proteins to enhance the response.
• Examples:
  • Hepatitis B vaccine (recombinant)
  • Human Papillomavirus (HPV) vaccine (recombinant)
  • Pneumococcal Conjugate vaccine (PCV)
  • Meningococcal Conjugate vaccine
  • Haemophilus influenzae type b (Hib) vaccine

4. Toxoid Vaccines

• Definition: These vaccines use toxins (or toxoids) produced by the pathogen. The toxins are inactivated but still trigger an immune response.
• Examples:
  • Diphtheria vaccine
  • Tetanus vaccine

5. mRNA Vaccines

• Definition: These vaccines use messenger RNA (mRNA) to instruct cells to produce a protein that triggers an immune response.
• Examples:
  • Pfizer-BioNTech COVID-19 vaccine
  • Moderna COVID-19 vaccine

6. Viral Vector Vaccines

• Definition: These vaccines use a harmless virus (different from the one that causes the disease) to deliver genetic material that teaches cells to make proteins that trigger an immune response.
• Examples:
  • Oxford-AstraZeneca COVID-19 vaccine
  • Johnson & Johnson COVID-19 vaccine
  • Ebola vaccine

7. DNA Vaccines (In Development)

• Definition: These vaccines use genetically engineered DNA to produce antigens and elicit an immune response.
• Examples: Many are in the experimental stages, like DNA vaccines for Zika virus and certain cancers.

These classifications highlight how different vaccines are tailored to effectively prevent diseases based on various mechanisms of stimulating the immune system.