Milkmaids and Vaccines

Lecture 2

Vaccine

• Substance that builds preventative immune protection against a specific infection

• Types:

  • Inactivated (killed)

  • Attenuated (weakened)

How long does vaccine development usually take?

• 10–15 years from concept to federal approval

Why are vaccines important?

• Extremely effective at preventing disease

• Have saved millions of lives

Example of vaccine success: Poliovirus

• Poliovirus infects nerve cells → causes paralysis

  • Early solution: Iron lungs

• Jonas Salk developed the polio vaccine → became very popular

What were plagues like before vaccines and antibiotics?

• Infectious diseases killed huge numbers of people

• Plagues shaped history (wars, populations)

What happened during the Plague of Athens (430 BC)?

• Athens vs. Sparta (war)

  • Spartans = good warriors, Athenians = big walls

• Plague hit Athens → 25–33% of population died

• Spartans didn’t avoid Athens → later conquered the weakened city

Who gave the earliest written description of immunity?

• Thucydides, physician during Plague of Athens

• Observed that people who recovered did not get sick again

• Quote: “the sick and the dying were tended by the pitying care of
  those who had recovered, because they knew the course of
  the disease and were themselves free from apprehensions.
  For no one was ever attacked a second time, or not with a
  fatal result"

Did Athenians understand germs?

• No → germ theory not known until 1860s (2300 years later)

• Instead, people believed in “miasma” (bad air theory)

What did John Snow discover in 1854?

• Investigated London cholera outbreak

• Found cause was contaminated water (not air)

• Removed pump handle → outbreak ended

• Suggested boiling water → led to modern water safety practices

• Couldn’t yet prove microbes caused it

What did Louis Pasteur discover between 1860–1864?

• Studied why wine & beer spoiled

• Discovered microorganisms caused spoilage

• Heating liquids (then cooling) killed microbes → prevented spoilage

• This process = Pasteurization

Why is pasteurization important?

• Greatly prolongs shelf life of milk

What was the main problem with early disease research?

No definitive proof that microorganisms caused disease

What did Robert Koch discover in 1876?

• Built microscope to look at bacteria

• Used microscopy + culture techniques → generated pure cultures of bacteria

• Published the first picture of bacteria (Anthrax)

• Showed anthrax bacteria caused disease in animals → Germ Theory proven

What are Koch’s Postulates?

1. A specific microorganism is always associated with a given disease

2. Microorganism can be isolated from diseased animal & grown in pure culture in lab

3. Cultured microbe causes disease when transferred to a healthy animal

4. Same microorganism can be re-isolated from newly infected animal

But… viruses can’t be re-isolated

How did Louis Pasteur accidentally discover immunity with chickens?

• Studied chicken cholera bacteria

• Assistant forgot to use fresh culture, injected old (weakened) bacteria → chickens survived

• Later, fresh bacteria injected → chickens immune and survived again

• Led to inactivated vaccines → basis for Salk’s polio vaccine

What was the relationship between Koch and Pasteur?

• Knew each other, rival scientists

• Teased each other’s work (pure cultures vs. pasteurization)

• Both made foundational discoveries in microbiology and immunity

Who was Paul Ehrlich and what did he discover around 1900?

• Studied anti-serum therapy (horse → human transfer) to cure diphtheria

• Proposed Side Chain Theory of Immunity → blood proteins protect against pathogens

• Thought immunity is: Adaptive (responds to infection) + Humoral (in blood)

• He was right → talking about antibodies (structure defined in 1959)

• Won Nobel Prize in 1908

Who was Eli Metchnikoff and what did he discover in 1883?

• Used microscopes to study starfish cells

• Found cells eating foreign material → called them “phagocytes” (later macrophages = big eaters)

• Proposed immunity is: Innate (pre-programmed and simple) + Cellular (cell-based protection)

• He was also correct

What are the two major arms of immunity?

• Innate immunity: hard-wired, evolutionarily conserved

  • Humoral (proteins in fluids)

  • Cellular (phagocytes, natural killer cells)

• Adaptive immunity: built for variability

  • Humoral (antibodies)

  • Cellular (T cells, B cells)

What disease was first eradicated by vaccines, and when?

• Smallpox → first vaccine in 1796, widespread immunization by 1800 (60 years before Pasteur’s work)

• WHO global vaccination campaign → eradicated in 1980

• No cases since

There is only one eradicated virus = smallpox

What did Edward Jenner do in 1796 with milkmaids and cowpox?

• Observed milkmaids who got cowpox were protected from smallpox

• Collected cowpox material from milkmaid Sarah Nelms → injected 8-year-old James Phipps

• James got mildly sick but recovered

• Later injected James with smallpox → fully protected, even on repeat exposure

• Jenner called it vaccination (from “vacca” = cow)

Was Jenner the only one who thought of vaccination?

• Others had noticed cowpox-smallpox link

• Jenner knew about variolation (giving smallpox to induce mild infection) and was variolated himself

  • Risky → many died

• Variolation practiced in China, India (16th century) and brought to England by Lady Mary Wortley Montagu (after seeing it in the Ottoman Empire - Turkey)

What’s the “clickbait” version of vaccination history?

• “Did England steal credit for vaccination from China?”

• Because variolation and early protective practices existed long before Jenner