Vaccines need to be stable for easy transport, which can be challenging, especially in remote areas without refrigeration.
The "cold chain" involves transporting vaccines with refrigeration to remote communities.
This increases complexity and cost.
Vaccines need to be affordable for all countries.
Global surveillance is crucial due to international mobility facilitated by organizations like the World Health Organization (WHO).
Current Eradication Efforts
Diseases targeted for eradication:
Polio
Measles
Rubella
Typhoid
Measles outbreaks are rising due to lack of vaccination.
Polio is close to eradication.
Polio Vaccines
Two types are available:
Inactivated or killed Salk vaccine (injected) IgG: Triggers an immune response and production of immunoglobulins like IgG and immune memory, but requires trained professionals for administration.
Attenuated or oral polio vaccine (OPV): Replicates in the gut, shedding vaccine-derived virus to immunize others in the community.
Oral Polio Vaccine (OPV) Details
OPV contains weakened strains of the virus that replicate in the intestine, building up antibodies (mucosal or intestinal immunity).
The weakened viruses excreted spread protection in the community by passively immunizing others.
OPV breaks the chain of infection and is easily administered by putting two drops into the mouth.
Inactivated Polio Vaccine (IPV) Details
Administered through injection and contains killed strains of the virus.
Produces antibodies in the blood but does little to stop the virus from spreading from the intestine to others.
Becomes more important as we move closer to a polio-free world.
Vaccination Coverage
Over 95% of people need to be vaccinated to halt polio circulation.
Global Polio Eradication Initiative strengthens routine immunization programs.
Challenges and Risks of OPV
The shared virus from OPV can spread via contaminated water/food sources.
In areas with low vaccination, the virus can undergo genetic mutations and revert to a paralytic form.
High vaccination levels and eventual withdrawal of OPV are necessary.
Polio Eradication in Africa
In August 2020, the WHO declared Africa free of wild polio after no cases since 2016.
Achieved through concerted efforts, reaching 95% vaccination coverage.
War and disturbances in the Middle East have caused a recent rise in polio cases.
Monitoring Polio
In Australia, monitoring includes:
Notification of symptomatic cases.
Wastewater testing in sewage plants for pathogens, including polio.
During COVID-19, wastewater testing also monitored COVID levels.
Herd Immunity
Community-based immunity achieved when sufficient population coverage prevents outbreaks.
For polio, 95% vaccination is the target.
Protects those who cannot be vaccinated, such as pregnant women, young children, and immunocompromised individuals.
Diagram illustrating reduced disease spread with high vaccination rates.
Infectious Diseases and Poverty
Main infectious diseases causing deaths:
Tuberculosis
Malaria
Diarrheal diseases (leading cause of death in children under 5 in developing countries)
Pneumonia
Measles
HIV/AIDS
These are often illnesses of poverty, related to cost-effectiveness of vaccination and treatment, education, sanitation, water and food sources, and waste disposal.
Example: HIV/AIDS in Africa where families may share medication due to cost, resulting in suboptimal doses and development of AIDS.
Types of Immunization
Passive Immunization:
Injection containing immunoglobulin Ig.
Preventative measure with preformed antibodies.
Provides quick protection but no long-term memory.
Used in antitoxins (tetanus, gas gangrene), hepatitis A, measles, and shingles vaccines.
Active Immunization:
Antigen introduced to the body.
Triggers cell-mediated and humoral immune responses.
Creates memory cells for quicker and greater response upon re-exposure.
Vaccine Mechanisms
Most vaccines contain a component of the microorganism that causes harm.
Live, killed, subunit, and mRNA vaccines are used.
COVID-19 Vaccines as Examples
AstraZeneca: Live, attenuated vaccine using an adenovirus modified to produce the spike protein of COVID-19.
Pfizer: mRNA vaccine containing the code for making the spike protein.
All vaccines introduce the immune system to the spike protein through different mechanisms.
Immunoglobulin Response IgM
Produced quickly upon exposure to the antigen.
Levels drop off rapidly. IgG
Main defensive immunoglobulin.
Produced a few days after exposure.
Levels drop over time but remain stable.
Booster shots increase IgG levels with each subsequent dose, leading to lifelong immunity in some cases.
Different organisms trigger responses to varying extents.
COVID-19 Vaccination and Immunoglobulin
COVID-19 vaccines target the spike protein, inducing IgG, IgM, and IgA.
IgA is distributed on mucosal surfaces (respiratory defense). * Booster shots mainly boost IgG, not IgA.
Vaccines reduce severe disease but are less effective at preventing transmission.
COVID-19 and Eradication Considerations
Not limited to humans (found in other animals).
Has asymptomatic carriers.
Has many variants.
Vaccine cost is high for some countries.
Effective at attenuating severe disease.
Considered a safe vaccine.
Global monitoring was inconsistent.
Disease is not easily detected (symptoms resemble flu, cold, or hay fever).
Vaccine requires cold storage.
Mandatory Vaccinations for Healthcare Workers
Healthcare workers are more likely to contact infectious organisms.
VU (College of Sport and Exercise Science) requires clinical placements to have: