7.2.4. Vaccination and Immunisation

The principle of immunisation or vaccination is based on the property of ‘memory’ of the immune system. In vaccination, a preparation of antigenic proteins of pathogen or inactivated/weakened pathogen (vaccine) are introduced into the body.

Vaccination leverages the immune system's ability to remember past infections. When a vaccine containing weakened or dead pathogens is introduced into the body, it stimulates the immune system to produce antibodies. This process creates an immunological 'memory' that allows the body to respond more effectively if exposed to the actual pathogen in the future.

Think of vaccination like a dress rehearsal for a play. The actors (immune cells) practice their lines (antibodies) so that when the actual performance (real infection) comes, they react appropriately and seamlessly.

The antibodies produced in the body against these antigens would neutralise the pathogenic agents during actual infection.

Antibodies are specialized proteins that the immune system creates in response to antigens found in pathogens. Once produced, these antibodies can recognize and bind to the pathogen during a real infection, marking it for destruction by other immune cells and preventing the disease from taking hold.

Consider antibodies as security guards in a mall. Once they recognize a suspicious person (the pathogen), they alert the rest of the security team to take action and prevent any potential harm.

The vaccines also generate memory – B and T-cells that recognise the pathogen quickly on subsequent exposure and overwhelm the invaders with a massive production of antibodies.

Vaccination leads to the generation of memory B and T cells specific to the pathogen. These memory cells remain in the body long after vaccination. Upon re-exposure to the same pathogen, these cells can spring into action quickly, producing large amounts of antibodies more rapidly than during the initial exposure. This rapid response prevents the illness from establishing.

Think of memory cells like a saved contact on your phone. Once you've saved a contact, you can call them immediately without searching for their details again. Memory cells allow for a fast and efficient response the next time the body encounters the same pathogen.

If a person is infected with some deadly microbes to which quick immune response is required as in tetanus, we need to directly inject the preformed antibodies, or antitoxin (a preparation containing antibodies to the toxin).

In situations where an immediate immune response is necessary, like in tetanus, healthcare providers may administer pre-formed antibodies directly. This form of protection is called passive immunisation. It does not create lasting immunity, but it provides immediate protection against the diseases.

Imagine you need to put out a fire quickly. Instead of waiting for a fire truck (which represents your immune system), you grab a fire extinguisher (antibodies) to handle the emergency right away. This is akin to passive immunisation.

Recombinant DNA technology has allowed the production of antigenic polypeptides of pathogen in bacteria or yeast. Vaccines produced using this approach allow large scale production and hence greater availability for immunisation, e.g., hepatitis B vaccine produced from yeast.

Recombinant DNA technology has enabled scientists to create vaccines that are both safe and effective. By using bacteria or yeast to produce parts of pathogen proteins, researchers can generate large quantities of vaccine components efficiently. This technology has revolutionized vaccine production, making vaccines more accessible to populations worldwide.

It's like using a factory that specializes in making thousands of toys instead of trying to craft each toy by hand. This factory allows for quicker production and more toys available for everyone, similar to how recombinant technology increases vaccine availability.

--