Vaccines

• Vaccines can eradicate a disease or block transmission and prevent symptoms.
• Vaccine safety:

  • Attenuated vaccines - vaccines with antigens that have been weakened to reduce the severity of the disease. Dangers: reversion to wildtype, foetal damage, persistent infection.
  • Non-living vaccine: vaccine with dead antigen. Dangers: allergic reaction, autoimmunity (body attacks own cells).
• Types of vaccine: Passive and active.

  1. Passive- Contains immune serum globulin (antibody against specific antigen). Gives immediate immunity so won't activate immune system. Meaning immunity is lost when antibody is broken down. Used post exposure to rabies or hepatitis A and B.
  2. Active- Contains either an inactivated antigen or a live antigen. Causes immune system to be activated and build antibodies in response to antigen. Gives lifelong immunity. Used for polio, measles and influenza.

  
• Adapting virus for vaccine: Virus grown in tissue culture (monkey kidney cells) and repeated sub passage mutations accumulate and the mutated strain that is least dangerous is selected.

  • Virus- grown in monkey kidney cells
  • Bacteria (mycobacterium)- grown in glycerol bile potato medium for 10 years.

  
• Influenza vaccine: Egg based production. Chicken eggs are infected with flu viruses which grow inside them. The egg white is then removed from the shell and used as the base for the vaccine.
• Living versus non-living vaccines: Living are attenuated whilst non-living are inactivated. Attenuated is cheaper and has longer immunity.

  
• Factors that favour global eradication of an infectious disease:

  1. Disease limited to Humans
  2. Few strains
  3. Cheap, effective vaccine available.

  
• Childhood immunisations: Pneumococcal and polio vaccine given at 2 months old and 4 months old. MMR given at 13 months old.

  
• BCG and Hep B vaccines:

  • BCG vaccine is a live attenuated vaccine that protects against tuberculosis. 70% effective but less effective against respiratory forms of the disease. Recommended for all children where the incidence of TB is 40/100,000. Or grandparents/parents born in country where TB is 40/100,000.
  • Hep B is inactivated part of hepatitis B virus and given in 3 doses. If pregnant women has hepatitis B then baby is given vaccine. Recommended for healthcare workers. Schedule of injection- 1st, 4 weeks 2nd, 6 months 3rd, 10 yrs booster.

  
• Pneumococcal vaccine: protects against pneumococcal infection that causes pneumonia and meningitis. Given to 65 years old and over. Recommended for adults and children that are at an increased risk of getting pneumococcal disease.
• Cervical cancer (HPV vaccine): Girls aged 12-13 are vaccinated against human papilloma virus which causes cervical cancer. There is also a 3 year catch up programme that offers the HPV vaccine to girls aged 13-18.

  
• Varicella zoster vaccine:

  • Protects against chickenpox and shingles. Recommended for non-immune health care workers to protect themselves and patients.
  • Health care workers who have never had chickenpox or shingles infection, get blood tested to check their immunity. If seronegative (no immunity) then vaccine is recommended.

  
• Influenza vaccine: Gives 70-80% protection against influenza. Less protection in elderly.

  
• Travelling: Each country has guidelines for which vaccinations are recommended or compulsory.

  
• MMR vaccine: Protects against measles, mumps and rubella. Given in 2 doses at 12-15 months and 4-6 years.
• Polio vaccine: Two types Salk (injection) and Sabin (oral). Salk is an inactivated version of virus whilst Sabin is an attenuated version of virus. Sabin can infect others and give them some immunity however the virus can revert to wildtype and cause polio. Salk can be used in children whilst Sabin cannot.

  
• HIV vaccine: Cannot be made as HIV attacks the immune system itself and there is is no effective cell mediated immune response.