What are VACCINES- types of vaccine-live and killed vaccine and its importance.

VACCINES :

Vaccine is an immuno – biological substance designed to produce specific protection against a given disease.

v It stimulates the production of protective antibody and other immune mechanisms.

v Vaccines may be prepared from live modified organisms, inactivated or killed organisms, extracted cellular fractions, toxoids or combination of these. More recent preparations are sub – unit vaccines and recombinant vaccines.

Types of vaccines:

They  are broadly divided into four types.

1.     Live vaccines :

They are preparations containing live microorganisms with reduced virulence.

Live vaccines (e.g. BCG ,measles ,oral polio) are prepared from live organisms. In general, live vaccines are more potent immunizing agents than killed vaccines.

a.      Live organisms multiply in the host and the resulting antigenic dose is larger than what is injected.

b.     Live vaccines have all the major and minor antigenic components.

c.      Live vaccines engage certain tissues of the body. As for example, intestinal mucosa by the oral polio vaccine:

Live vaccines should not be administered to persons with “ immune deficiency disease” or to persons whose immune response may be suppressed because of leukemia, lymphoma or malignancy or because of therapy with corticosteroids, alkylating agents, antimetabolic agents, or radiation.

Pregnancy is another contraindication unless the risk of infection exceeds the risk of harm to the foetus of some live vaccines.

Live vaccines must be properaly stored to retain effectiveness.

Serious failures of measles and polio vaccines have resulted from inadequate refrigeration prior through.

Example :

Live vaccines

1.     Bacterial live vaccines

·        BCG for tuberculosis

·        Typhoid , plague.

2.     Viral vaccines

·        Oral polio

·        Yellow fever

·        Measles

·        Rubella

·        Mumps

·        Influenza

·        Killed cholera vaccine .

2.     Killed vaccines :

They are preparations containing killed or inactivated microorganisms.

They are prepared by inactivation of microorganisms by heat, phenol, fumerine  etc.

Example :

Tab for enteric fever, cholera, whooping cough, plague, rabies, influenza.

Killed or inactivated vaccines :

Bacterial

1.     Typhoid

2.     Cholera

3.     Pertussis

4.     Meningitis

5.     Plague

Viral :-

1.     Rabies

2.     Salk (polio).

3.     Influenza

4.     Hepatitis B

5.     Japanase encephalitis .

3.     Toxoid :

v Certain microorganisms produce exotoxins, e.g. Diphtheria and tetanus bacilli.

v These toxins can be detoxified and used for immunization.

v The detoxified toxin is known as toxoid, which is non toxic but antigenic e.g. TT, DT, DPT.

BACTERIAL TOXOIDS :

·        Diphtheria tetanus

4.     Combined vaccine :

If more than one kind of immunizing agent is included in the vaccine, it is called “ a mixed or combined vaccine”.

The aim of combined vaccines is to simplify administration, reduce costs and minimize the number of contacts of the patient with the health system.

The following are some of the well-known combinations.

These are vaccine preparations containing more than one immunizing agents.

e.g.

  DPT (Diphtheria , pertussis, tetanus).

MMR (Mumps, measles,rubella).

DPTP (DPT+Polio).



IMMUNIZATION SCHEDULE 

Indian immunization schedule