INTRODUCTON AND DIFFERENTIATION BETWEEN LIVE AND KILLED VACCINE.

 

INTRODUCTON AND DIFFERENTIATION        BETWEEN LIVE AND KILLED VACCINE.

 

Vaccine:

Vaccine is a biological preparation that provides active acquired immunity to a particular infectious disease. A vaccine typically contains an agent that resembles a disease-causing micro-organism and is often made from weakened or killed forms of the microbe, it’s toxin or one of its surface proteins. The agent stimulates the body’s immune system to recognize the agent as a threat, destroy it, and to further recognize and destroy any of the micro-organism associated with the agent that it may encounter in future. The first vaccine was discovered by EDWARD JENNER in 1798 A.D. against smallpox. Vaccination is the procedure of introduction a safe antigen into a host to induce immunity against infection.

TYPES OF VACCINE:

There are two types of vaccine i.e. Whole agent vaccine and Subunit vaccine. The Whole agent vaccine is further divided into Attenuated or Live vaccine and Inactivated or Killed vaccine.

ATTENUATED OR LIVE VACCINE: Attenuated or Live vaccine is created by reducing the virulence of a pathogen, but still keeping it viable (live) and the organism still replicates. It is maintained by adapting the pathogen in an unfavorable condition and the organism still replicates. Attenuation is achieved by growing the pathogen in an unnatural host by passaging in non-homologous host (host cell) for repeated period of time (i.e. 70-80 times) or in different physical condition. Attenuation may also be done by adapting the virus to grow in a temperature lower than normal temperature. The process of reducing the virulence and retaining the immunogenicity is called attenuation.

INACTIVATED OR KILLED VACCINE: Inactivated or killed vaccine is prepared by physical or chemical treatment to the pathogen so that the organism become inactive and loses the replication capability. The procedure should not disturb the immunogenic structures or epitopes, but should remove the replication or virulence of the organisms. Chemical treatment is done by the use of formaldehyde, glutaraldehyde, beta propiolactone etc. while the physical treatment is done by the use of gamma radiation, UV radiation etc. It requires an adjuvant to increase the potency of the vaccine and multiple doses.

 

                DIFFERENCE BETWEEN LIVE AND KILLED VACCINE             

Comparative Feature	Live/ Attenuated vaccine	Inactivated/ killed vaccine
1. Safety	Some risks (reversion to virulent, fetal infection, contaminating micro-organism)	Usually safe (unlikely to contain contaminating micro-organism
2. Stability	Affected by temperature, sunlight and short shelf	Stable on storage
3. Onset of immunity	Rapid	Slow
4. Duration of immunity	One year or longer	Usually short (one month)
5. Antibody response	IgM, IgG, IgA	Predominantly IgG
6. Cell mediated response	Good	Poor
7. Locally secretory immunity	Usually present	Absent
8. Antigenic dose	Low	High
9. Route of administration	Natural or by injection	By injection only
10. Number of doses	Single (Usually)	Multiple (Booster)
11. Adjuvant	Not required	Required
12. Maternal antibody influence	Very significance	Minimal effect
13. Cost	Low	High