vaccination

active immunity

• lymphocytes are activated by antigens that enter the body

• a specific immune response is produced

passive immunity

• antibodies are introduced into the body and provide immunity

• no activation of lymphocytes occurs

vaccination

• antigens are introduced into the body in order to produce a specific immune response

• results in ARTIFICAL ACTIVE IMMUNITY

• a vaccine is a preparation containing antigenic material

• it is introduced into the body by injection or orally

types of vaccines

1. live

2. dead

3. subunit

4. genetically engineered

live

• living whole microorganism

• attenuated (harmless or weak version)

dead

• dead whole microorganism

subunit

• contains some part of product of microorganisms

• eg inactivated toxins (toxoids)

• isolated surface antigens eg proteins

genetically engineered

• genetically engineered antigens

primary and secondary response to vaccine

reasons for vaccines

• epidemics= when a disease spreads rapidly and affects many people

• pandemic= when a disease spreads over a very large area eg continent and whole world

• heard immunity= majority of a populations immune to a particular disease

how is herd immunity formed

1. routine vaccinations- given to majority of young children in UK in order to provide herd immunity

2. Ring vaccination- used during epidemics to control the spread of disease- all individuals in contact with the initial case are vaccinated

problems with vaccines

• poor response

• antigenic variation

• eukaryotic pathogens

• antigenic concealment

• safety concerns

poor response

• some don’t respond well

• reasons: malnutrition and immunodeficiency

antigenci variation

• some pathogens mutate regularly (influenza virus) to give different antigens

• new antigens may not be recognised by body’s memory cell

• antigenic drift= minor

• antigenic SHIFT= major

eukaryotic pathogens

• eukaryotic pathogens are more complex than bacteria or viruses

• they may have many more antigens and a complex life cycle making vaccine development difficult

• eg plasmodium (malaria)

antigenic concealment

• some pathogens hide in host cells + so reduce the time available for an immune response

  • eg plasmodium (malaria)

safety concerns

• vaccines cause side effects

• certain individuals may be hypersensitive or allergic to either the antigen or other ingredients in the vaccine