VACCINES

• 1. LIVE – ATTENUATED VACCINES (LAV)
  2. Available since the 1950s, live attenuated vaccines (LAV) are derived from disease- causing pathogens (virus or bacteria) that have been weakened under laboratory conditions.
  3. They will grow in a vaccinated individual, but because they are weak, they will cause no or very mild disease.
• • 2. INACTIVE VACCINES (KILLED ANTIGEN)
  • Inactivated vaccines are made from microorganisms (viruses, bacteria, other) that have been killed through physical or chemical processes. 
  • These killed organisms cannot cause disease.
• • 3. SUBUNIT (PURIFIED ANTIGEN)
  • Protein-based subunit vaccines
  • Protein based subunit vaccines present an antigen to the immune system without viral particles, using a specific, isolate protein of the pathogen.
  • A weakness of this technique is that isolated proteins, if denatured, may bind to different antibodies than the protein of the pathogen.
• • 3. SUBUNIT (PURIFIED ANTIGEN)
  • Polysaccharide vaccines
  • Some bacteria when infecting humans are often protected by a polysaccharide (sugar) capsule that helps the organism evade the human defense systems especially in infants and young children.
  • Polysaccharide vaccines create a response against the molecules in the pathogen’s capsule. These molecules are small, and often not very immunogenic. As a consequence, they tend to:
  • Not be effective in infants and young children (under 18–24 months)
  • Induce only short-term immunity
• • 4. TOXOID (Inactivated Toxins)
  • Toxoid vaccines are based on the toxin produced by certain bacteria.
  • The toxin invades the bloodstream and is largely responsible for the symptoms of the disease.
  • The protein-based toxin is rendered harmless (toxoid) and used as the antigen in the vaccine to elicit immunity.