Vaccine

CEP - Fundamentals of Infection and Diseases Synchronous Discussion

History of Vaccine

Origin of Vaccine and its History

  • The fall of smallpox began long before modern medicine:

    • 1022 A.D.: A Buddhist nun in O Mei Shan, Sichuan, China, used variolation by grinding smallpox swabs and blowing them into uninfected persons.

    • Variolation: An early method of inoculating someone with the smallpox virus to produce immunity, recognized as the precursor to modern vaccination.

Evolution of Variolation Method

  • Evolved in the 1700s:

    • Doctors used material from smallpox sores, applying it to uninfected individuals through 4 or 5 scratches on the arm.

Edward Jenner's Observations

  • Noticed dairy maids had immunity to smallpox:

    • A dairy maid noted they would not get smallpox after already having cowpox.

    • Cowpox: A skin disease resembling smallpox that infects cows, leading to Jenner's hypothesis that exposure could provide immunity.

Jenner's Experiment

  • May 1796 A.D.: Jenner used cowpox sample from dairy maid Sarah Nelmes:

    • Inoculated James Phipps, an 8-year-old boy, with cowpox lesions.

    • Two months later, he inoculated James with smallpox, and James did not develop the disease.

    • This experiment established a method for preventing smallpox.

Vaccine Development

Goals of Vaccine Development

  • Two main goals:

    • Safety: Ensuring the vaccine is safe for human use.

    • Efficacy: Effectiveness in preventing disease and infection.

Stages of Clinical Trial

  • Animal Phase: Initial testing on animals to monitor side effects and efficacy, and to inoculate with the virus.

  • Phase I:

    • Vaccine administered to healthy humans (fewer than 100 participants).

    • Monitored for side effects and determined dosage limits (upper limit for side effects, lower limit for antibody response).

  • Phase II:

    • Involves 100-1,000 participants including healthy individuals and those with comorbidities, matching demographics for study.

    • Continued monitoring of side effects and effective dosage needed.

  • Phase III:

    • Expanded trials on human subjects to assess efficacy by matching demographics and monitoring COVID-19 symptoms via PCR tests for positive/negative results.