(7a) Immunisation Flashcards
Vaccination is the most effective medical intervention, second only to what?
Access to clean water
What happened in 1796 in the history of immunisation?
Edward Jenner - inoculation with cowpox virus for protection against smallpox
What happened in 1860s-1890s in the history of immunisation?
Louis Pasteur - produced vaccines against chickenpox, cholera, diphtheria, anthrax and rabies
What happened in the early 20th century in the history of immunisation?
Toxoid vaccines against diphtheria and tetanus produced following discovery of effective inactivation with chemicals
What happened post WW2 in the history of immunisation?
Successful live viral vaccines developed using cell culture technique
WHO estimated that how many deaths in 2008 in children under 5 were due to diseases that could’ve been prevented by routine vaccination?
1.5 million
17% of global total mortality in children under 5 years of age
6.6 million children under 5 died in 2012. 58% were due to what?
Infectious diseases - globally biggest cause = pneumococcal infection
What is the strategic aim of vaccination?
- selective protection of the vulnerable
- elimination (herd immunity)
- eradication
What is the programmatic aim of vaccination?
- prevent deaths
- prevent infection
- prevent transmission (secondary cases)
- prevent clinical cases
- prevent cases in a certain age group
- to reduce mortality and morbidity from vaccine preventable infections
Why immunise?
- prevent individual disease (life-long, not just children)
- ideally halt carriage and transmission (herd immunity)
- ideally eliminate then eradicate disease
- high coverage is operational target
What are the non-specific immune defences?
- unbroken skin
- mucous membranes of gut and lungs
- acid and enzymes of gut
- non-specific metabolism/inactivation
What is involved in innate immunity?
- complement
- WBCs
- cytokines
What is involved in immune system memory?
- immunoglobin (initially non-specific)
- learns specific IgG response
- lays down immune memory
Give an example of passive immunity?
Transfer from mother to unborn baby
Vertical transmission of auto-antibodies from mother to foetus and in breast-feeding
What do “maternal antibodies” do?
They can protect the baby for up to a year against illnesses to which the mother is immune
Give an example of a maternal antibody
IgG
Give an antibody that can be injected into somebody who needs them
IgG
Contains antibodies pooled together from the blood of many donors, can be injected into a person who needs antibodies
Is passive immunity effective?
Effective but usually disappears within several weeks or months
Most types of transfused blood contains antibodies
What is active immunity?
Long-lasting immunity produced by the immune system in response to antigens
Active immunity responds to antigens. Where can these come from?
Can be from natural infection or from vaccinations - the immune system makes antibodies to help destroy these antigens
What is the benefit of vaccination in terms of active immunity?
In vaccination, active immunity occurs without disease or disease complications
What is “immunological memory”?
The persistence of protection for many years after natural infection or vaccination
B cells persist with the ability to recognise the specific antigen and so can produce IgG antibodies more quickly and in greater numbers
What is an antigen?
Anything that can be bound by an antibody
Antibodies interact specifically with relatively small parts of molecules. What are these known as?
Antigenic determinants or epitopes
What is an epitope?
An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. For example, the epitope is the specific piece of the antigen that an antibody binds to
Antibodies are produced to one specific antigen. Give some examples of different antibodies
IgM
IgG
IgA
IgE
The primary immune response develops in the weeks following the first exposure to an antigen. Which antibody does it involve?
Mainly IgM
The secondary immune response is faster and more powerful. Which antibody does it involve?
Mainly IgG
Which cells are antibodies produced by?
B lymphocytes
What triggers clonal expansion of the antibody?
Antigen binds non-specifically to variable region of the antibody molecule - this triggers clinical expansion
What happens after antigen binding?
1st wave of IgM production
Followed by IgG production
What facilitates the destruction of the antigen-bearing micro-organism?
IgG binds tightly to antigen and through simultaneous complement binding facilitates the destruction of the antigen-bearing micro-organism
What happens when infection resolves?
Levels of IgG decline
However, one set of the IgG producing B cells persist with the ability to recognise that specific antigen
Passive immunity can be vertical transmission from mother to baby or injection of human immunoglobin. Give examples of injection of human immunoglobin
- HNIG - pooled plasma
- specific - tetanus, botulism, hep B, rabies, varicella
Give examples of diseases where the live (attenuated) organisms is used in vaccination
- MMR
- BCG
- yellow fever
- varicella
They act like the natural infection
Give examples of diseases where the inactivated organisms are used in vaccination
- pertussis
- typhoid
- IPV
Give examples of diseases where components of the organisms are used in vaccination
- influenza
- pneumococcal
Give examples of diseases where the inactivated toxins are used in vaccination
- diphtheria
- tetanus
What are the advantages of using live vaccines?
- single dose often sufficient to induce long-lasting immunity
- strong immune response evoked
- local and systemic immunity produced
What are the disadvantages of using live vaccines?
- potential to revert to virulence
- contraindicated in immunosuppressed patients
- interference by viruses or vaccines and passive antibody
- poor stability
- potential for contamination
What are the advantages of using inactivated/killed vaccines?
- stable
- constituents clearly defined
- unable to cause the infection
What are the disadvantages of using inactivated/ killed vaccines?
- need several doses
- local reactions common
- adjuvant needed (keeps vaccine at injection site, activated antigen presenting cells)
- shorter lasting immunity
What are the types of local reactions that might occur in vaccination?
Local - pain, swelling or redness at injection site, small nodules may form at injection site
What are the types of general reactions that might occur in vaccination?
Fever, irritability, malaise, fatigue, headache, nausea, vomiting, diarrhoea, loss of appetite
In live vaccines, does the frequency of reactions increase or decrease with increasing number of doses?
Decreases
Ab produced in response to live vaccine neutralises the small amount of vaccine virus in subsequent vaccine dose
In inactivated vaccines, does the frequency of reactions increase or decrease with increasing number of doses?
Increases
If Ab levels are good from earlier vaccination, Ab binds to the vaccine antigen in a subsequent dose leading to an inflammatory response
When do vaccine reactions normally occur in inactivated vaccines?
Generally within 48 hours following vaccination
When do vaccine reactions normally occur in live vaccines?
Occur according to time taken for virus to replicate
When do vaccine reactions occur in the MMR vaccine (live vaccine)?
Reactions to measles component - 1st week following vaccination
Reactions to rubella component - 2nd week following vaccination
Reactions to mumps component - 3rd week following vaccination (although may occur up to 6 weeks following vaccination)
What reaction does the MMR vaccine cause?
Measles component - malaise, fever, rash
Rubella component - pain, stiffness or swelling of joints
Mumps component - parotid swelling
What is the routine NHS vaccination programme?
2 months = DTaP/IPV/Hib + pneumo + rota
3 months = DTaP/IPV/Hib + Men C + rota
4 months = DTaP/IPV/Hib + pneumo
12 months = HiB/Men C + MMR + pneumo
24-48 months = annual flu
40 months = DTaP/IPV + MMR
12 years = HPV for girls
14 years = Td/IPV + Men C
65 years = penumo + annual flu
70 years = shingles
At what age is the first dose of MMR given?
12 months
Give some recent changes in the UK childhood immunisation schedule
- added more serogroups to pneumococcal vaccination
- cease universal adolescent BCG
- HPV (and cervical cancer)
Give some relatively new vaccines
- varicella/zostavax
- menveo
- men B
- rotavirus
- fluenz
What is a toxoid?
A toxoid is a bacterial toxin (usually an exotoxin) whose toxicity has been inactivated or suppressed
