What Is Immunity? Types Of Immunity and Vaccination

What Is Immunity?

Immunity is defined as the ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitized white blood cells.

Immune system:

The immune system is a complex network of cells and proteins that defends the body against infection. 



These specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity. Human beings have four types of immunity — innate, adaptive, active and passive: Innate immunity: Everyone is born with innate (or natural) immunity, a type of general protection.


The main parts of the immune system are: white blood cells, antibodies, the complement system, the lymphatic system, the spleen, thymus, and bone marrow.


It is common for people to have an over- or under active immune system. auto immune or allergic disorders.

Type of immunity:

1.Active immunity:

Individuals rely on active immunity more than passive immunity. Luckily, most of our exposures are to agents that will not result in disease, either because they are harmless or because our immune system works to neutralize them.
In addition to “fighting off” these pathogens, active immunity is important because it lasts a long time in the form of immunologic memory


an individual who recovers from a first case of the measles is immune to further infection

2.Passive immunity:

Passive immunity, or immunity gained in a way other than from one’s own immune system, can occur in a few ways and can be life-saving. However, passive immunity is short-lived because the antibodies are not continually replenished as they would be in an individual whose immune system is responding directly. Passive immunity can occur in a couple of ways:
Maternal antibodies
Unborn and newly born babies are protected by antibodies from the maternal immune system. These antibodies are shared in two ways: across the placenta and in breast feeding.


Passive immunity can occur naturally, such as when an infant receives a mother’s antibodies through the placenta or breast milk, or artificially, such as when a person receives antibodies in the form of an injection (gamma globulin injection).

3.Innate immunity:

Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen’s appearance in human body. 
The innate immune system is made of defense against infection that can be activated immediately once a pathogen attacks. The innate immune system is essentially made up ofbarriers that aim to keep viruses, bacteria, parasites, and other foreign particles out of your body or limit their ability to spread and move throughout the body.


  • Examples of innate immunity include:
  • Cough reflex
  • Enzymes in tears and skin oils
  • Mucus, which traps bacteria and small particles
  • Skin
  • Stomach acid

4.Acquired immunity:

The adaptive immune system, also referred as the acquired immune system, is a subsystem of the immune system that is composed of specialized, systemic cells and processes that eliminates pathogens by preventing their growth. The acquired immune system is one of the two main immunity strategies found in vertebrates.


The placental transfer of IgG from mother to fetus during pregnancy that generally lasts 4 to 6 months after birth.

Vaccines and Immunizations-Types of Vaccines:


Anti-rabies vaccine:-

The vaccine is liquid preparation of Rabies fixed virus grown in Yero cells.


The vaccine shall be shaken homogeneously before use.
2.5 I.U. 0.5% 60-90Jlg


The deltoid muscle of the upper arm is the recommended site for I.M. administration.


Store and ship at 2-8°C. Protect from light.

Validity period:

18 month. 

Anti-snake venom:

Anti-Snake venom serum is a sterile preparation containing purified and concentrated immunoglobulins obtained from the serum of healthy horses immunized against the venoms of the following four common poisonous snakes of Pakistan namely:
1. Cobra
2. Krait
3. Russell’s viper
4. Saw scaled viper


Conventionally the dose of Anti-Snake Venom Serum is 10-30 ml and in severe cases it may go up to 200 ml.


Once the venom has got into the circulation, it is the anti-snake venom serum that can neutralize it.
At first the dose of 10-30 ml of the serum will be injected intravenously very slowly.


The product is potent for two years from the date of manufacturing if kept at 2-8°C. Room temperature deteriorates the protein contents of anti-snake venom serum.

Measles vaccine:-


One dose of 0.1ml of measles vaccine.


Vaccine should be administered subcutaneously.


Freeze dried vaccine should be stored between 2 and 8 degrees celsius.

Typhoid vaccine:-


The initial dose is 0.5 ml. and the 2nd dose should be of 1.0 mi.


The route’ of Injection IS preferably subcutaneously.


The product should be stored at 4-8 Celsius In’ refrigerator.

Tetanus vaccine:


0.5ml intra-muscular injection at any age.


Three doses of 0.5ml each, the first two doses are to be given 4-8 weeks apart with a third dose 6 to 12 months later. To maintain the level of immunity, further 0.5ml booster dose is recommended every 5to 10years.


Store between +2 to +8’C, protect from light, do not freeze and do not use inadvertently frozen vaccine.

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