Types of vaccines
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There are several types of vaccines: 1. Live attenuated vaccines which use weakened live pathogens. Examples include vaccines for tuberculosis, polio, measles, rotavirus, and yellow fever. 2. Inactivated/killed vaccines which use killed pathogens. They are more stable than live vaccines but more expensive, such as the inactivated polio vaccine. 3. Toxoid vaccines which use detoxified bacterial toxins like those for tetanus and diphtheria. 4. Subunit vaccines which contain only antigenic parts of pathogens like the hepatitis B vaccine. Conjugated subunit vaccines link antigens to polysaccharides to help immature immune systems respond. Examples are vaccines for Hib and
Types of vaccines
- 2. 1. Live Attenuated Vaccines (LAVs) • LAVs are derived from (already weekened) disease-causing pathogens (virus/bacteria). • 5 vaccines (recommended by WHO) using LAV technology – Tuberculosis (BCG) – Oral Polio Vaccine, paralytic poliomyelitis. – Measles – Rotavirus – Yellow Fever
- 3. 2. Inactivated/ Killed Vaccine • Made from (already killed via physical/chemical processes) microorganism (virus/bacteria). Therefore, non-disease causing. • More stable than LAVs. • Example: – Inactivated polio vaccine (IPV) more expensive than OPV-LAV
- 4. 3. Toxoid Vaccine • Bacterial toxins like tetanus & diphtheria, detoxified/purified toxins are called toxoids, used in vaccines. • Example. – Tetanus Toxoid (TT) – Diphtheria Toxoid (DT and Td)
- 5. 4. Subunit (Purified antigen) Vaccine • Like inactivated vaccines. • Contains only the antigenic parts/fragments of the pathogen (virus/bacteria). • Further categorized into – Protein-based subunit vaccines – Polysaccharide vaccines – Conjugate subunit vaccines • Example. – Hepatitis B Vaccine
- 6. 5. Conjugated (Subunit) Vaccine • Vaccine from conjugated/linked antigens or toxoids by polysaccharides (coatings). – used for infants and younger children • The linkage(conjugation) helps the immune system (immature) react to polysaccharide coatings (disguise) and protect them from disease-causing bacterium. • Example. – Haemophilus influenza type b conjugate (Hib) – Pneumococcal Conjugate (PCV-7, PCV-10, PCV-13), pneumococcus
- 7. 6. Nucleic Acid (DNA) Vaccine • Still in experimental stages • Vaccines containing DNA, microbes'genetic material that codes for certain antigens that is administered directly into the body by injection. • Example. – DNA Vaccine against West Nile Virus Encephalitis, an infectious disease (1999) by infected mosquitoes with West Nile virus.