W14 Vaccines and Immunity (GN) Flashcards
what is the definition of a vaccine?
What form is it administered in?
- A biological preparation designed to induce body’s natural immune response produce specific protection against an infectious agent → Immunisation
- Usually, prevention measure
- Administered in liquid form (injection/oral), or by intranasal routes.
- Acquired active immunity form
What is Passive immunisation?
- Protection provided by administering immune components (typically antibodies) in a host produced by another organism (external source).
- Immediate protection against infection
- Temporary protection → no memory immune cells are established
Examples of Passive immunisation? (2)
- Natural
* Antibodies received by an infant from the mother
▪ Across the placenta (last 1-2 months of pregnancy)
▪ via breast milk - Artificial
* Injection of antibodies or serum (for rapid protection when an individual is at immediate risk
▪ snake antivenom or antitetanic serum
What is Active immunisation?
- Protection generated by a person’s immune system to an antigen
- Induces immunological memory against a pathogen’s antigen
- Provides long-lasting protection (years, decades), with exceptions (malaria, SARS-CoV-2)
- Takes time to develop → immunisation to develop a mature response
Principles of adaptive immunity:
Initial immune response:
* Occurs after first infection
* A slow rise in antibody prevalence and T-cell activation is observed.
* Peaks around day 14, followed by a decline by day 21
Protective Immunity:
* Established after the initial response.
* Antibody levels and T cell numbers decrease but remain above baseline.
* Protects against reinfection for a period (several weeks).
Immunological Memory:
* Lasts for years following the first infection.
* Characterized by memory B and T cells.
* In case of reinfection:
-Rapid and robust secondary response.
-Prevents significant symptoms, often resulting in mild or inapparent reinfections.
Active vs passive immunisation:
Achieved by:
P- Transfer of antibodies produced by other hosts
A- Host’s own immune system
Time lag to provide protection:
P- Immediate
A- Takes time (days-weeks)
Immune memory
P- No
A- Yes
Duration of protection
P- Only short-term
A- Longer/long-term (usually)
Examples
P- Antitetanic serum
A- Tetanus vaccine
What are the Properties of an ideal vaccine?
- Safe
- Provide long-last protective immunity
- Triggering humoral and cell-mediated immune response
- Should not induce autoimmunity
- Practical consideration
-not expensive
-relatively easy to store and manufacture - Must be perceived as safe ( Reducing vaccine hesitancy factors And contrast conspiracy theories)
General components of a vaccine:
- Active components → vaccine antigen(s)
- Excipients (diluents/buffers, stabilisers, preservatives, trace components)
- Excipients (diluents/buffers, stabilisers, preservatives, trace components)
- Antibiotics
Active components:
what is their role as an ingredient of a vaccine?
- Consists of a non-infectious, altered, or partial form of the microorganisms (or a related toxin).
- Serves as an antigenic stimulus to train the immunity to swiftly response against them and develop immunological memory
- This ensures a swift protection if the actual pathogens are encountered later
Adjuvant:
what is their role as an ingredient of a vaccine?
- Safe substances to strengthen and lengthen the immune response to the vaccine
- To reduce booster jabs and lower doses of antigens
- Mechanism:
➢Inducing an inflammation response that stimulates the recruitment & activation of immune cells to the injection site→ onset of mild side effects
➢Slow release of antigen at the inoculation site
Example
▪ MF59 is a mixture of oil, water and squalene (natural product from plant and animal cells → immunogenic properties)
Scheme of vaccination:
What is a Primary vaccination?
What is a Booster vaccination?
▪ One dose vaccines (BCG, variola, measles, mumps, rubella, yellow fever)
▪ Multiple dose vaccines (polio, DPT, hepatitis B)
To maintain immunity level after it declines after some time has elapsed (DT, MMR).
What is Herd immunity?
- Vaccine confer protective immunity against a microorganism at an individual level, but in certain circumstances also at a community level.
- Herd immunity → Population scale vaccination (when enough people in a stable community are vaccinated)
- Principle: microbial spread stops when the probability of infection drops below a critical threshold
- Essential to protect immunocompromised patients
- Not always feasible → SARS-CoV-2
Herd immunity:
Environmental Factors: (2)
- Environmental Factors:
▪ crowded conditions within a population
▪ seasonal variations - Strength of Individual’s Immune System and microbial-specific immune duration
- Infectiousness of Disease: greater the risk of infection, the higher percentage of people need vaccines to attain herd immunity
- Vaccine efficacy:
-the reduction in incidence of a disease amongst vaccinated people relative to the incidence in the unvaccinated. Rarely, vaccines are 100% effective
Herd immunity and large-scale vaccination campaigns: (for info)
- Smallpox was eradicated through a large-scale vaccination campaigns
- It killed about 300 millions of people in the 20th century
- highly infectious, with no known cure
- Smallpox vaccine was introduced by Edward Jenner in 1796
- Used cowpox virus to protect against
smallpox - Basis for modern vaccination
Smallpox eradication
- Smallpox was eradicated by achieving sufficient immunization coverage (herd
immunity within the global population) - Smallpox eradication program launched 1967 and eradicated 1979
- For a microorganism eradication, two essential criteria:
▪ Replication in only one host
▪ Vaccination induces lifelong immunity
