What are the Types of Immunity?

Internal medicine hospital in Bangalore

 What is Immunity?

Immunity is the body’s ability to resist infection, For Simpler understanding, immunity is the protection as a result of any infection or vaccination. 

Antibodies, as the name suggests are The “Opposing Force” developed by (us / host) against any infection. These antibodies are manufactured specifically to deal with antigens (Component Protein particles of any micro-organism). 

Types of Immunity

There are two types of immunity:

1. Natural Active Immunity: It is derived after an active infection and is called Natural Active Immunity. Its duration of protection is long term and we also are protected in our early childhood by the antibodies which are acquired by us by Trans placentally or via the breast milk, the Natural Passive Immunity e.g. Mother’s milk with protective antibodies- IgG for various infections, its duration of protection is short term. The two types of Natural immunity generally described are that of Cell-Mediated and Antibody-Mediated ones.

2. Acquired Immunity: There are two types of acquired immunity.

  • Artificial - Active Immunity: Due to vaccination, its protection is specific to the protein component and the organism and the protection is usually long-term ( lifelong in some cases). 
  • Artificial - Passive Immunity: Immune globulin administration and its duration of protection are usually short-term. This method is used in the treatment of Rabies, and also the treatment of children exposed to Chicken Pox.

Natural Active Immunity means when our own immune cells actively involve in the production of antibodies against a particular disease (In the process of recovery from an Infection) or against a protein component (Vaccine) & offer long-term protection e.g. Recovery from Infections and Response to vaccines….Polio, Chickenpox, Pneumococcal, etc.

Passive Immunity: When readymade antibodies are administered without the involvement of our body’s immune system and offer immediate but short-term protection e.g.  Immunoglobulins. Consult with an Internal medicine doctor in Bangalore for passive immunity.

Immunization: It is the process of production of immunity by artificial means.

What is Vaccination?

Vaccination is the act of administering a vaccine to individuals, whereas the term Immunization implies that a protective response has occurred. Vaccination is available at Manipal, regarded as the best internal medicine hospital in Bangalore

Who introduced immunization?

The first disease for which vaccination was produced was smallpox. The smallpox vaccine was first invented in 1796 by English physician Edward Jenner. Louis Pasteur advanced the concept through his work in microbiology. The immunization was called vaccination because it was derived from a virus affecting cows (Latin: ’Vacca 'cow').[

There are 4 main types of vaccines:

  • Live-attenuated vaccines

  • Inactivated vaccines

  • Subunit, recombinant, polysaccharide, and conjugate vaccines

  • Toxoid vaccines

The development of a vaccine is a tedious but very gratifying process. The two most important aspects of developing a vaccine are that we need to understand the Pathogen (Organism) & the Pathogenesis (Mechanism by which it affects us). In-depth knowledge of this should enable us to zero in on the Possible Protein components which are critical to cause the disease or design mechanisms to inactivate the organism. We later develop these structures either the protein components or the inactivated or killed organisms in the lab, which when administered to individuals provide immunity. 

Alternatively, we develop mechanisms to weaken the organism to the point that it cannot cause the disease but have enough strength in them to elicit an immune response from the host, thereby helping us develop immunity, the Live Attenuated Vaccine.

Stages of Vaccine Development & Testing

First Step: Laboratory and Animal Studies: It has Exploratory Stage 2-4 years.

Pre- Clinical studies: 1-2 years use tissue or cell culture systems and animal testing for safety, immunogenicity, and Immune response.

IND Application: Submission of application for Investigational New Drug, consist of description about manufacturing, testing processes, a summary of a lab report, description of proposed studies, an institutional review board, representing an institution where clinical trials will be conducted, must approve the clinical protocol. FDA takes 30 days to approve this. After IND approval, the vaccine is subject to 3 phases of testing.

Clinical studies with Human Subjects

Phase I vaccine Trials: Involves a small group of adults 20 -80 subjects, Safety and immune response, a promising Phase1 trial will progress to the next stage.

Phase II Vaccine Trial: Involves several hundreds of adults, these trials are randomized and well-controlled and include placebo group, Safety, immunogenicity, proposed dose, schedule of immunizations, and method of delivery.

Phase III Vaccine Trials:  Successful Phase II candidate vaccines move on to larger trials which involve thousands to tens of thousands of people. These phase tests are randomized & double-blind and involve the experimental vaccine being tested against a placebo (saline solution). The goal is to assess vaccine safety in a large group as it might be possible that certain rare side effects might not surface in the smaller groups.  

Vaccine efficacy is tested, like prevention of disease, does it prevent infection with the pathogen, does it lead to the production of antibodies or other types of immune responses related to the pathogens.

Next Step: Approval & Licensure. After licensure also FDA / DCGI monitors the manufacture’s production of the vaccine, testing of vaccine potency, safety and purity.  FDA does its own testing if needed.

Post -Licensures Monitoring of Vaccine: They include Phase IV trials, the vaccine adverse event reporting system, and Vaccine Safety Datalink.

Phase IV Trials are optional studies conducted by drug companies after the vaccine is released to test the vaccine safety, efficacy and other potential use.

VAERS: The Vaccine Adverse Event Reporting System: Detect new, unusual or rare vaccine adverse events, monitor any increase in known adverse events, identify potential risk factor for the particular type of adverse event.


Dr. Manohar K N

Consultant – Internal Medicine

Manipal Hospitals Bangalore – Old Airport Road

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