Different Types of Vaccines

Abstract

Vaccines can be classified according to their nature into the following types: ● Inactivated vaccines: ■ Whole organism; ■ Acellular extracts. ● Live attenuated vaccines. ● Toxoid vaccines. ● Subunit vaccines. ● Conjugate vaccines. ● DNA vaccines. ● Recombinant vector vaccines. Inactivation of the whole organism is the most basic form of vaccine produced by killing the micro-organism causing the disease using heat, chemical or radiation and presents all the antigens in the inactivated organism as a vaccine to induce immunity in the recipient. Other methods to produce an inactivated vaccine is by extracting acellular components of the organism through filtration. Examples of inactivated bacterial vaccines currently in use include: ● Anthrax—sterile filtrate from cultures of the Sterne strain of B. anthracis. ● Cholera—oral inactivated vaccine with 1mg of recombinant cholera toxin B (rCTB) in a liquid suspension of four strains of killed V. cholerae O1, representing subtypes Inaba and Ogawa and biotypes El Tor and classical. ● Pertussis—acellular vaccine has replaced previously used whole cell vaccine. ● Typhoid—purified Vi capsular polysaccharide from S. typhi; NB: the injectable, killed, whole-cell typhoid vaccine which contains heat-inactivated, phenol-preserved S. typhi organisms is no longer in use in the UK. Examples of inactivated viral vaccines currently in use in the UK include: ● Hepatitis A virus. ● Hepatitis E virus. ● Influenza A and B viruses. ● Japanese encephalitis virus. ● Polio viruses 1, 2, and 3 (IPV). ● Rabies virus. ● Tick-borne encephalitis virus. ● Bacterial vaccines: Bacillus Calmette-Guerin (BCG) vaccine is a live attenuated vaccine against tuberculosis derived from a Mycobacterium bovis strain. The oral typhoid vaccine contains a live attenuated strain of S. typhi (Ty21a) in an enteric-coated capsule. ● Viral vaccines: The measles, mumps, and rubella (MMR) vaccine contain live attenuated strains of measles, mumps, and rubella viruses, which are cultured separately and mixed before being lyophilized. Oral polio vaccine (OPV) against polio viruses 1, 2, and 3—OPV contains live attenuated strains of poliomyelitis virus types 1, 2, and 3 grown in cell cultures.