Types of vaccines

VACCINE {ACTIVE IMMUNOPROPHYLAXIS}
Vaccine is an immunobiological preparation that provides specific protection against a given disease.
Following vaccine administration, the immunogen (active ingredient of the vaccine) stimulates the immune system of the body to produce active immunity in the form of protective antibody/immunocompetent T cell response.

HISTORY
The terms vaccine and vaccination are derived from '' Variolae vaccinae'' (smallpox of the cow) the term devised by Edward Jenner in 1796 to denote cowpox.

TYPES OF VACCINES
1. LIVE ATTENUATED VACCINE: They are prepared from live (usually attenuated) organism that lose the bility to induce full blown disease, but retain their immunogenicity.
e.g. BCG vaccine, measles.
2.INACTIVATED/KILLED VACCINE: It consist of organisms which are grown in culture under controlled conditions, and the killed by using methods like heat or formaldehyde.
e.g. Typhoid vaccine, Salk vaccine (IPV)

3. TOXOID VACCINE: The exotoxins produced by certain bacteria can be detoxicated to form toxoid by treating with acidic pH, formalin or by prolonged storage.
e.g. Diphtheria toxoid, Tetanus toxoid.
4.SUBUNIT VACCINE: For certain viruses only a particular subunit of the virus is necessary to initiate the infection, e.g. Hepatitis B surface antigen (HBsAg) is the immunogenic component of hepatitis B virus.
e.g. Human Papillomavirus vaccine (HPV)

5.COMBINED VACCINE: If more than one immunizing agents are included in vaccine preparation, it is called combined vaccine.
e.g. in DPT vaccine, the pertussis component acts as an adjuvant, which increases the immunogenicity of both diphtheria toxoid and tetanus toxoid.