Principles of immunisation Flashcards
Describe the principles of active and passive immunisation.
Active Immunization: Stimulates the immune system to produce its own antibodies, leading to long-lasting immunity through memory cells. Examples include vaccinations.
Passive Immunization: Provides immediate but temporary protection by transferring pre-formed antibodies without stimulating the recipient’s immune system. Examples include antibody therapies and immunoglobulin injections.
PROS AND CONS OF EACH:
PASSIVE;
Advantages
Gives immediate protection
A quick fix
Disadvantages
Short term effect – no immunological memory
Serum sickness – incoming antibody is recognised as a foreign antigen by the recipient and results in anaphylaxis
Graft versus host disease (cell grafts only) – incoming immune cells reject the recipient
ACTIVE;
Advantages
Antigen (whole organism or part of it) stimulates immune response
Long term immunity – may be lifelong
Immunological memory
Disadvantages
No immediate effect, but faster and better response to next antigenic encounter
Describe the types of vaccine available for active immunisation.
- Inactivated (Killed) Vaccines
Description: Contain pathogens that have been killed or inactivated so that they cannot cause disease.
Examples:
Inactivated Polio Vaccine (IPV)
Hepatitis A Vaccine
Characteristics: Generally safe and stable, but may require multiple doses to achieve full immunity. - Live Attenuated Vaccines
Description: Contain live pathogens that have been weakened (attenuated) so they cannot cause disease in healthy individuals.
Examples:
Measles, Mumps, Rubella (MMR) Vaccine
Yellow Fever Vaccine
Characteristics: Often provide strong, long-lasting immunity and usually require fewer doses, but may not be suitable for immunocompromised individuals. - Subunit Vaccines
Description: Contain only specific parts of the pathogen (such as proteins or sugars) rather than the whole organism.
Examples:
Hepatitis B Vaccine (contains the surface protein)
Human Papillomavirus (HPV) Vaccine
Characteristics: Generally safe and well-tolerated, but may require adjuvants to enhance the immune response and often need multiple doses. - Toxoid Vaccines
Description: Contain inactivated toxins produced by certain bacteria. They stimulate immunity against the toxin rather than the bacteria itself.
Examples:
Diphtheria Toxoid Vaccine
Tetanus Toxoid Vaccine
Characteristics: Provide immunity against the effects of the toxin, requiring booster doses for long-lasting protection. - mRNA Vaccines
Description: Contain synthetic messenger RNA (mRNA) that instructs cells to produce a harmless piece of the pathogen (typically a protein) that triggers an immune response.
Examples:
Pfizer-BioNTech and Moderna COVID-19 Vaccines
Characteristics: Quick to develop, elicit strong immune responses, and can be tailored rapidly to emerging pathogens. - Viral Vector Vaccines
Description: Use a harmless virus (not the one that causes the disease) as a vector to deliver genetic material from the pathogen, prompting an immune response.
Examples:
Johnson & Johnson’s COVID-19 Vaccine (uses an adenovirus vector)
Ebola Vaccine (rVSV-ZEBOV)
Characteristics: Can induce strong immune responses and are stable for storage, but may have pre-existing immunity to the vector.
Define what is meant by the term vaccination
Vaccination is the administration of antigenic material (a vaccine) to stimulate an individual’s immune system to develop adaptive immunity to a pathogen.
Describe the contra-indications to vaccination
Temporary
Febrile illness
Pregnancy – cannot be given live attenuated vaccines
Permanent
Allergy
Immunocompromised – cannot be given live attenuated vaccines as individuals may develop disease from the vaccine strain
Describe how an immune response occurs
- Recognition of Pathogen
Antigen Presentation: When a pathogen enters the body, its antigens (molecules that provoke an immune response) are detected by immune cells.
Dendritic Cells and Macrophages: These antigen-presenting cells (APCs) capture the pathogen and process its antigens, presenting them on their surface using major histocompatibility complex (MHC) molecules. - Activation of T Cells
Migration to Lymph Nodes: The APCs migrate to the nearest lymph nodes, where they interact with naïve T cells.
T Cell Activation: If a T cell’s receptor (TCR) recognizes a specific antigen presented by the APC, it binds to it, resulting in:
Clonal Expansion: The activated T cell proliferates and differentiates into various subtypes, including:
Helper T Cells (CD4+ T Cells): Assist other immune cells.
Cytotoxic T Cells (CD8+ T Cells): Directly kill infected cells. - Activation of B Cells
Helper T Cell Support: Activated helper T cells release cytokines that stimulate B cells, which may also recognize the same antigen directly.
B Cell Activation: Upon activation, B cells proliferate and differentiate into:
Plasma Cells: Produce antibodies specific to the pathogen.
Memory B Cells: Provide long-term immunity. - Antibody Production
Antibody Secretion: Plasma cells secrete large quantities of antibodies (immunoglobulins) into the bloodstream. Antibodies bind to specific antigens, leading to:
Neutralization: Blocking the pathogen’s ability to infect cells.
Opsonization: Marking pathogens for destruction by phagocytes.
Activation of Complement System: Triggering a cascade that enhances inflammation and helps lyse pathogens. - Elimination of Pathogen
Phagocytosis: Phagocytic cells (like macrophages and neutrophils) engulf and digest pathogens coated with antibodies.
Cytotoxic T Cell Action: Cytotoxic T cells recognize and kill infected cells directly by inducing apoptosis (programmed cell death). - Resolution of the Immune Response
Regulation and Homeostasis: Once the pathogen is cleared, the immune response is downregulated to prevent overreaction and damage to host tissues. Regulatory T cells play a crucial role in this process.
Apoptosis of Effector Cells: Most effector T and B cells undergo apoptosis, while memory cells remain to provide a faster response in future encounters with the same pathogen. - Memory Formation
Long-term Immunity: Memory B cells and memory T cells persist long after the infection has been cleared. Upon re-exposure to the same pathogen, these memory cells can rapidly mount a strong and swift immune response, often preventing illness.
Describe the concept of herd immunity
- Vaccinated individuals are less likely to be a source of infection to others
- Reduces the risk of unvaccinated individuals being exposed to infection
- Individuals who cannot be vaccinated will still benefit from routine vaccination programmes
This is Herd immunity;
e.g. babies < 2 months are too young to be immunised, but are at the greatest risk of dying from whooping cough.
They were felt to be protected because older siblings and other children have been immunised and so would not pass on the infection.
Describe the vaccination schedules for children
2 months Diphtheria, tetanus, pertussis, polio, Haemophilis influenzae type b, Streptococcus pneumoniae, rotavirus
3 months Diphtheria, tetanus, pertussis, polio, Haemophilis influenzae type b, Neisseria meningitidis C, rotavirus
4 months Diphtheria, tetanus, pertussis, polio, Haemophilis influenzae type b, Streptococcus pneumoniae,
12-13 months Haemophilis influenzae type b, Neisseria meningitidis C, measles, mumps, rubella, Streptococcus pneumoniae
2/3/4 years Influenza
>3 years 4 months Diphtheria, tetanus, pertussis, polio, measles, mumps, rubella
12-13 years Human papilloma virus (females only)
13-18 years Diphtheria, tetanus, polio, Neisseria meningitidis C
Non-routine, at birth
Tuberculosis (BCG) Children who are more likely to come into contact with tuberculosis
Hepatitis B Children with hepatitis B positive mother
Describe the vaccines that may need to be given to travellers
Hepatitis A
Typhoid
Neisseria meningitidis serogroups A, C, W135, Y
Cholera
Yellow fever
Japanese encephalitis
Tick-borne encephalitis
Rabies
