TYPES OF VACCINE

Subject : Science & tech

Context : Pfizer has reported that its vaccine, BNT162b2, has been more than 90 per cent effective in late-stage trials.

Concept :

• This is a vaccine that was developed using mRNA technology — it makes use of the messenger RNA molecules that tell cells what proteins to build. The mRNA, in this case, is coded to tell the cells to recreate the spike protein of the novel coronavirus.

Types of Vaccine :

Inactivated Vaccines

• Active pathogens are grown in large numbers and then killed either by a chemical or heat. Although the pathogen is killed, or made to lose its reproduction capacity, various parts of the pathogen are intact. E.g The antigen (the chemical structure) that is recognised by the immune system is left unimpaired.
• When this dead microbe is introduced in the body, the immune system is tricked to respond by producing antibodies against specific antigens still left intact, without knowing that the pathogen is defective.
• As the pathogen is dead, it cannot reproduce nor cause even a mild disease. Thus, it is safe to administer to even people with lesser immunity, like the old and those who have comorbidity.
• Inactivated polio vaccine and the rabies vaccine are made this way.

Live-attenuated vaccines

• Live vaccines use a weakened (or attenuated) form of the germ that causes a disease.
• Because these vaccines are so similar to the natural infection that they help prevent, they create a strong and long-lasting immune response.
• Just one or two doses of most live vaccines can give you a lifetime of protection against a germ and the disease it causes.
• The limitation of this approach is that these vaccines usually cannot be given to people with weakened immune systems
• Live vaccines are used against: Measles, mumps, rubella (MMR combined vaccine), Rotavirus, Smallpox among others.

Subunit, recombinant, polysaccharide, and conjugate vaccines

• They use specific pieces of the germ — like its protein, sugar, or capsid (a casing around the germ). They give a very strong immune response.
• They can also be used on people with weakened immune systems and long-term health problems.
• These vaccines are used to protect against: Hib (Haemophilus influenzae type b) disease, Hepatitis B, HPV (Human papillomavirus), Pneumococcal disease among others.

Toxoid vaccines

• Toxoid vaccines use a toxin made by the germ that causes a disease. Toxoid vaccines are used to protect against: Diphtheria, Tetanus.