Overview of Vaccines and Their Impact

Aug 18, 2024

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Lecture on Vaccines: Prevention of Viral Diseases

Introduction to Vaccines

  • Misconception: Vaccines prevent disease, not infection.
    • During COVID-19, there was a misconception that vaccines would prevent infection.
  • Role of Vaccines: Enhance immune memory and defense against viruses.
    • Significant in increasing life expectancy.
    • Life expectancy from 1900 to now increased from 50 years to around 80.

Impact of Pandemics on Life Expectancy

  • 1918 Pandemic: Decreased life expectancy significantly.
  • COVID-19 Pandemic: Life expectancy dropped by 1.5 years in 2020.

Function of Vaccines

  • Immune Response: Vaccines stimulate both B and T cell memory.
    • Immune memory allows for rapid response upon re-exposure to a virus.

History of Vaccination

  • Smallpox: Variolation in China, Jenner's cowpox vaccine.
  • Vaccination Development: Pasteur's rabies vaccine, other vaccines for yellow fever, influenza.

Vaccine Skepticism and Anti-vaccine Movements

  • Historical and Current Resistance: Antivaccine sentiments from Jenner’s era to present.
  • Impact of Anti-vaccine Activists: Spread misinformation for profit.
    • Example: Joe Mercola’s misinformation during COVID-19.

Types of Vaccines

  • Active Vaccines: Use modified pathogen components to induce immunity.
  • Passive Vaccines: Use antibodies for short-term protection.
    • Examples: Maternal antibodies, convalescent plasma for COVID-19.

Requirements for Effective Vaccines

  • Immune Response: Correct Th1 or Th2 response.
  • Protection: Must protect against disease and be safe.
  • Long-term Immunity: Desirable for lasting protection.

Types of Vaccines and Production Methods

  • Inactivated Vaccines: Chemically inactivated viruses (e.g., polio, influenza).
  • Subunit Vaccines: Only parts of the virus used (e.g., Hepatitis B, HPV).
  • Attenuated Vaccines: Live but weakened virus (e.g., flu mist, OPV for polio).

Challenges with Eradication Using Vaccines

  • Polio Eradication: Difficult due to asymptomatic spread and vaccine-derived cases.
    • Vaccine-Derived Polio: Reversion of attenuated viruses causing paralysis.
  • Smallpox Eradication: Achieved due to single host and no asymptomatic spread.

Innovative Vaccine Technologies

  • New Delivery Methods: Micro-needle patches for self-administration.
  • Thermostable Vaccines: Stabilization using sugars for storage without refrigeration.

Conclusion and Future Directions

  • Addressing Vaccine Hesitancy: Important for public health success.
  • Research and Development: Continued innovation needed for better vaccines, especially for hard-to-eliminate diseases like polio.
  • Next Topic: Discussion on antivirals as another virus infection treatment method.

These notes summarize the key points discussed in the lecture on vaccines, including their development, impact, types, challenges, and future directions in vaccine technology.