Is Vaccination a key to Immunization?

Do you think vaccination and immunization mean the same? Vaccination is the administration of a vaccine to help the immune system develop protection from disease. It is an intentional exposure to different forms of a pathogen that do not cause disease. Vaccines contain microorganisms or viruses in a weakened, live attenuated or killed state or even in the form of proteins or toxins from the pathogenic organism.

Immunization is the process of eliciting a particularly long-lived state of protective immunity against a disease-causing pathogen. Exposure to the live pathogen followed by recovery is one route to immunization.

Vaccination and immunization both work in antigen-specific lymphocytes mechanisms and result in the generation of memory cells, providing long-lived protection. A key point to focus on here is vaccination does not ensure immunity significantly.  

“Vaccination is an event, whereas immunization (the development of a protective memory response) is a potential outcome of that event.”

To begin with, the principle of immunization or vaccination is based on the property of ‘memory’ of the immune system. The vaccines generate memory B and T cells that recognize the pathogen quickly on subsequent exposure and there is a massive production of antibodies. 

Passive Immunization:

The aim of passive immunization is transient protection or particularly alleviation of an existing condition. It is achieved by the delivery of preformed antibodies to a person. This occurs naturally when maternal IgG antibodies reach the developing fetus via the placenta. Basically, antibodies to Diphtheria, Rubeola, Rubella, Tetanus, Streptococci, Mumps and Poliovirus tend to pass to the developing fetus. Consequently, maternal antibodies present in early breast milk (called colostrum) also provide a crucial role to provide passive immunity to the young ones in the form of maternally produced IgA. Another type of passive immunization is seen in the form of antiserum that can also be achieved by injecting a recipient with preformed antibodies from immune individuals. (called antiserum). 

To conclude, if a person is infected with some deadly microbes to which a quick immune response is required as in Tetanus, we need to directly inject the preformed antibodies, or antitoxin (a specialized preparation containing antibodies to the toxin). Even in the cases of snakebites specifically, the injection which is administered to the patients contains preformed antibodies against the snake venom. 

Source: https://microbenotes.com

Active Immunization (Based on vaccination and immunization):

To emphasize, it includes the concept of immunity and memory. The main goal of active immunization is to trigger the adaptive immune response of our body in a way that will in turn elicit protective immunity and immunologic memory. In the case of active immunization, further exposure to the pathogen triggers a secondary immune response that successfully eliminates the pathogen or prevents disease mediated by its antigens. Another key point is that active immunization can be achieved by natural infection with a pathogen.  It can be acquired as artificial active immunity by the mechanism of vaccination.

Types of Vaccines:

As per the current pandemic situation of Covid-19, we must acquire some knowledge about the types of vaccines, as stated by WHO | World Health Organization. 

1. Whole organism approach

Live Attenuated Vaccines:

The live-attenuated vaccines are based on a living but weakened version of the pathogen or even the one that’s very alike. This may not be as effective for people with compromised immune systems. 

Source: https://www.who.int

Inactivated or ‘killed’ Vaccines

The disease-causing pathogen is treated using heat/chemicals/radiation. This kills the pathogen, making it incapable of replication. However, it still allows the pathogen to induce an immune response in the body of the host particularly. 

Source: https://www.fraunhofer.de

Source: https://www.who.int

2. Macromolecules approach

Subunit vaccines

Subunit vaccines are based upon specific parts called the subunits of a pathogen like a virus or a bacterium which are recognized by the immune system of the host.  They do not contain whole microorganisms. Another key point is that the subunits used may be antigenic proteins or sugars. 

Source: https://www.who.int

3. Genetic approach 

Recombinant Vector Vaccines

Individual genes that encode key antigens of especially virulent pathogens can be introduced into specialised vectors. The attenuated organisms usually serve as vectors and in this case, which is subsequently inserted in the host organisms.

DNA Vaccines

DNA vaccination is a more recent vaccination strategy that utilizes plasmid DNA having antigenic protein sequence that are injected directly into the host. This strategy is based on the fact that the host cells to take up the DNA and produce the immunogenic protein in vivo.

To summarize, do not forget- “Vaccination is an event, whereas immunization (the development of a protective memory response) is a potential outcome of that event.”

Hope the article helped you gain some knowledge about vaccination and immunization in the pandemic situation.

Thank you for reading at MBD. 

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