Summary Vaccinations

Vaccination I

Aims of Vaccination

 Block transmission and preventing symptoms of disease
 Protect individual against symptoms or pathology

Requirements

 Effective, safe, stable and cheap
 Effective:
 Humoral and cell mediated response required for resistance to intra and inter
cellular pathogens
 Don’t want activation of cytotoxic T cells
 Duration:
 Short term not adequate
 Need induction of immunological memory
 Diseases with longer incubation periods is better as immune system has time to
respond
 Immunological memory can be boosted if outbreaks of the disease takes place
 Live vaccines induce a stronger longer lasting immunity
 Safety:
 May cause disease
 Cant administer to immunosuppressed patients
 May be contaminated
 Stability:
 Need shelf-life
 Cold storage between factory and clinic
 Cost:
 Cheap enough for developing countries

Types of Vaccines

 Pathogens with reduced virulence artificially (attenuated)
 Pathogens with reduced virulence in humans naturally
 Killed organisms
 Cellular fragments of pathogens

Passive Immunisation

 Injection of purified antibodies or antibody containing serum to provide rapid,
temporary protection or treatment
 Natural passive immunity – maternal IGs through breast milk
 Used for:
 Prevent disease after exposure
 Reduce symptoms of on-going disease
 Protect immune deficient patients
 Block bacterial toxins and prevent disease they may cause
 Examples:
 Prophylaxis – Hepatitis A, Diphtheria and Tetanus
 Post exposure – Rabies, Hepatitis B and Measles
 Prophylaxis in immune deficient patients – Varicella Zoster
Active Immunisation

,  Administration of live vaccines or inactivated pathogens
 Attenuated vaccines:
 Selection of mutant pathogens (inactive)
 Attenuated by passage through cell cultures or chemically
 Oral Polio vaccine:
 Passed though monkey kidneys or human embryo fibroblasts
 Virulence checked by signs of nephrotoxicity in monkeys
 Inactivated vaccines:
 Killed or inactivated pathogens by heat or chemicals
 Used when live vaccines aren’t possible or appropriate for patient
 Sometimes attenuation cant be achieved as the pathogen reactivates
 Advantages – not infectious and relatively safe
 Disadvantages – lower immunogenicity so several doses needed for lasting
immunity, contaminated by toxins, allergic reaction or autoimmunity
 Cellular fragments:
 Protective immunity against a specific part of a pathogen – polysaccharide
capsule of Pneumococci or coating of HBV
 Can remove DNA/RNA from pathogen
 Bacterial toxins can be inactivated chemically – toxoids (Diphtheria and
Tetanus)
 DNA vaccines:
 DNA and promoter
 Not used in humans yet
 Possible oncogene insertion

Living vs Non-Living Vaccination




Vaccination II