What is a Vaccine?
- A vaccine is a biological preparation that offers active acquired immunity to a specific disease.
- Generally, a vaccine comprises of an agent that has a resemblance to the disease-causing microbe.
Types of Vaccine
- Inactivated Vaccine
- Vaccines of this type are created by inactivating a pathogen, typically using heat or chemicals such as formaldehyde or formalin.
- This destroys the pathogen’s ability to replicate but keeps it “intact” so that the immune system can still recognize it.
- Attenuated Vaccine
- Some of the most common methods involve passing the disease-causing virus through a series of cell cultures or animal embryos (typically chick embryos).
- When the resulting vaccine virus is given to a human, it will be unable to replicate enough to cause illness, but will still provoke an immune response that can protect against future infection.
- Toxoid Vaccine
- Toxoid vaccines prevent diseases caused by bacteria that produce toxins (poisons) in the body.
- These have weakened forms of toxins called toxins in them.
- Subunit Vaccine
- Subunit vaccines use only part of a target pathogen to provoke a response from the immune system.
- This may be done by isolating a specific protein from a pathogen and presenting it as an antigen on its own.
- Conjugate Vaccine
- Conjugate vaccines use part of the coating of bacteria called polysaccharides.
- It is a type of subunit vaccine that combines a weak antigen with a strong antigen as a carrier so that the immune system has a stronger response to the weak antigen.
- Examples include hepatitis B, HPV
- Valence Vaccine
- A monovalent vaccine is designed to immunize against a single antigen or single microorganism.
- A multivalent or polyvalent vaccine is designed to immunize against two or more strains of the same microorganism, or against two or more microorganisms.
- Heterotypic Vaccine
- Heterologous vaccines also known as “Jennerian vaccines”, are vaccines that are pathogens of other animals that either do not cause disease or cause mild disease in the organism being treated.
- mRNA Vaccine
- An mRNA vaccine (or RNA vaccine) is a novel type of vaccine which is composed of the nucleic acid RNA, packaged within a vector such as lipid nanoparticles.