Vaccination and Infectious Diseases

Objectives

• Describe how vaccines reduce the spread of infectious diseases.
• Explain the concept of herd immunity.
• Discuss potential issues related to people choosing not to be vaccinated.

Overview

• Vaccines: Widely used in medicine to prevent epidemics and pandemics.
• Epidemic: Rapid spread of disease in a specific area or country.
  • Example: 2019–2020 measles epidemic in New Zealand.
• Pandemic: Rapid spread across multiple countries or globally.
  • Example: COVID-19 pandemic.

How Vaccines Work

• Administered orally or by injection.
• Contain antigens from pathogens to trigger immune response.
  • Attenuated strains: Weakened but can cause a mild infection.
  • Inactivated pathogens: Cannot cause infection but stimulate immunity.
  • Antigen molecules: Extracted or genetically engineered.
  • Toxins: Modified to be harmless but still act as antigens.

Immune Response

• Primary immune response: Production of antibodies and memory B cells.
• Secondary immune response: Rapid production of antibodies upon re-exposure to the pathogen, preventing symptoms.
• This is artificial active immunity.

Herd Immunity

• Protects unvaccinated individuals (e.g., young children, immunocompromised) by surrounding them with vaccinated individuals.
• Requires a high percentage of vaccinated people to be effective.
• Breakdown occurs if a significant number of people are unvaccinated, leading to potential outbreaks.

Vaccination Practices & Challenges

• UK routine vaccinations: Flu vaccines for over 50s or those with health issues; children vaccinated against various diseases.
• Global vaccination efforts during pandemics (e.g., COVID-19).

Effectiveness

• Varies by disease:
  • Influenza virus: Mutates frequently, requiring annual vaccination due to antigenic variability.
  • Common cold: Over 100 virus types with varying antigens, making vaccination ineffective.

Conclusion

• Vaccination is key in preventing the spread of infectious diseases through both direct protection and herd immunity.
• Essential to maintain high vaccination rates to prevent epidemics.

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