principles of immunisation Flashcards
what are the different types of immunity
immunity is either adaptive or inate
adaptive immunity can be active or passive
active immunity can be natural (infection or exposure) or passive (immunisation)
passive immunity can be natural (placental transfer of IgG or colostral transfer of IgA) or passive (immunoglobulin therapy or immune cells)
advantages passive immunity
immediate protection quick fix
disadvantages of passive immunity
- short term effect - no immunologcal memory - serum sickness - incoming antibody is recognised as a foreign antigen by the recipient resulting in anaphylaxis - graft vs host disease (cell grafts only) - incoming immune cells reject the recipient
natural passive immunity example
maternal immunoglobulins can be transferred to the foetus or neonate naturally using a specialised mechanism involving the neonatal Fc receptors
artificial passive immunity examples
snake or spider bites, scorpion or fish stings: passive infusion of antibody specific for the toxin. Hypogammaglobulinemia: 1y/2y infusion of gamma-globulins to reduce infection. Rabies immunoglobulin: post-exposure prophylaxis together with vaccination
where can immunoglobulin be used for post-exposure prophylaxis
- Human normal immunoglobulin (HNIG): Hep A, measles, polio, rubella - Specific immunoglobulins: Hep B, rabies, tetanus, varicella-Zoster virus
active immunity types
Natural - exposure/infection, artificial - vaccination
what stimulates active immunity
- Antigen (whole organism or part of it) stimulates immune response
what are some of the benefits of active immunity
- Long term immunity - may be lifelong - Immunological memory - No immediate effect, faster and better response to next antigenic encounter
how is immunisation related to active immunity
The administration of antigenic material (a vaccine) to stimulate an individual’s immune system to develop adaptive immunity to a pathogen
name 3 common diseases vaccinated against
measles, mumps and rubella MMR vaccine
what are the 4 types of vaccines
killed whole organism, attenuated whole organism, subunit vaccines, toxoid vaccines
what are killed whole organism vaccines
target organism (e.g. polio virus) is killed (must be completely killed in order to be effective and not cause disease) effective and relatively easy to manufacture booster shots likely to be required,
what are attenuated whole organism vaccines
(mainly viruses): an avirulent strain of target organism is isolated can be very powerful and better than killed vaccines, stimulate natural infection, reversion back to virulent form is possible refrigeration required
what is circulating vaccine derived polio virus
Acute paralysis derived from the vaccine-virus which genetically mutates into a form that can paralyse, occurs in seriously under-vaccinated populations where the excreted vaccine-virus can circulate for an extended period of time
what are subunit vaccines
- Recombinant proteins - have the structure of the virus but no genetic material so they can’t infect ○ Generally very safe ○ Easy to standardise ○ Not very immunogenic w/o effective adjuvant ○ Need to understand how to generate immunity
what are toxoid vaccines
- Toxin is treated with formalin - Toxoid retains antigenicity but has no toxic activity - Only induces immunity against the toxin not the organism that produces it - E.g. tetanus, diphtheria
5 examples of live attenuated vaccines
- Tuberculosis - BCG - oral polio vaccine - measles - rotavirus - yellow fever
2 examples of killed antigen vaccines (attenuated)
- whole cell pertussis - inactivated polio virus
2 examples of toxoid vaccines
tetanus toxoid diphtheria toxoid
4 examples of subunit vaccines
- acellular pertussis
- haemophilus influenzae type B
- pneumococcal
- hepatitis b
temporary contraindications of vaccination
febrile illness, pregnancy - can’t be given live attenuated vaccine as it could cause problems in the foetus
permanent contraindications of vaccination
allergy, immunocompromised - can’t be given live attenuated vaccines as the individual may develop the disease from the vaccine strain
what is herd immunity
- 1y aim of vaccination is to protect the individual who receives the vaccination - Vaccinated individuals are less likely to be a source of infection to others which reduces the risk of unvaccinated individuals being exposed to infection - Individuals who can’t be vaccinated will still benefit from routine vaccination programmes - 95% coverage is ideal as this prevents spread of infection
what are 4 properties of a good vaccine
- Potent antibody response
- high antibody titers
- Potent CD8+ cytotoxic T cell response
- CD4+ T helper response Memory
what are the challenges facing vaccines
- Persistence - ideally vaccines should give life long protection - Generation of memory cells
- Protection of vulnerable groups: young, elderly and immunocompromised
- Antigenic shift and drift, strain diversity: bird and swine influenza pandemics
- The cold chain network
what is antigenic shift
2 or more different strains of a virus OR a strain of 2 or more different viruses combine to form a new subtype having a mixture of the surface antigens of the original strains
it is a major change and can lead to epidemics
what is antigenic drift
small changes in the proteins produced by the virus, minor changes from year to year, they arise from point mutations
what is the cold chain network
- Purpose of the vaccine cold chain is to maintain product quality from the time of manufacture until the point of administration by ensuring vaccines are stored and transported within WHO recommended temp ranges Important to maintain the viability of the vaccine
what are the challenges regarding neonates and vaccination
- Vulnerability <18-24 mths to encapsulated bacteria e.g. pneumococcus, Hib and meningococcus - Fewer FDC and B cells don’t express costimulatory molecules - Short term antibody production
what are the challenges regarding the elderly and vaccination
- Reduced efficacy or responsiveness to vaccination - Oligoclonal responses lacking specificity Reduced plasma cell several niches in the bone marrow
what are conjugate vaccines
- Antigen is the carbohydrate capsule - Carbs are poor antigens (don’t stimulate the immune system as broadly as protein antigens), esp in babies - Conjugation of the carb to a protein carrier makes them more effective (generates a much more powerful immune response) - E.g. Streptococcus pneumoniae, Haemophilus influenzae type b, Neisseria meningitidis C
HPV as a vaccine for cancer
- Cervical cancer is the 2nd most common cause of female cancer death - HPV linked to 100% of all cervical cancers (has also been linked to head and neck cancers) - Complete protection against >70% of cancer causing HPV strains Currently 3 vaccines are available - protect against different numbers of strains
checkpoint inhibitors
- Checkpoint inhibitor antibodies unlock the gateway to the adaptive immune system
- Boosts the immune resopnse
- Powerful anti-tumour responses
- Potential for immune related adverse effects
- Immunotherapy is a type of cancer treatment that helps your immune system fight cancer.
example of herd immunity
babies < 2mths who are too young to be immunised but are at the greatest risk of drying from whooping cough, they were felt to be protected because older siblings and other children have been immunised and so wouldn’t pass on the infection
what is meant by high antibody titers
(how much antibody an organism has produced that recognises a particular epitope - the part of an antigen molecule to which an antibody attaches itself
