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Two breakthroughs began to defeat disease: Jenner's vaccination against smallpox, and Pasteur's germ theory, which at last explained what actually caused infection.
From inoculation to vaccination
- Before Jenner, people used inoculation (variolation): deliberately giving someone a mild dose of smallpox from a sore, which built protection but could kill them or spread the disease.
- Lady Mary Wortley Montagu saw inoculation used in the Ottoman Empire and introduced it to Britain in the 1720s.
- Edward Jenner noticed that milkmaids who caught mild cowpox never caught deadly smallpox.
- In 1796 he gave a boy cowpox, then exposed him to smallpox and he did not fall ill. Jenner published in 1798 and named it vaccination, from vacca, the Latin for cow.
How vaccination spread
- Vaccination met strong opposition: some feared using material from a cow, some said disease was God's will, and inoculators feared losing their income.
- It spread anyway, because it plainly worked and then won government backing.
- Parliament rewarded Jenner with money in 1802, and vaccination against smallpox was made compulsory in Britain in 1853.
- Jenner never knew why it worked, only that it did, so it stayed a one-off cure rather than a method that could be copied for other diseases.
Pasteur and the germ theory
- Until the mid-1800s people blamed disease on miasma (bad air), or thought germs simply appeared by themselves, an idea called spontaneous generation.
- Louis Pasteur, studying why wine and beer turned sour, showed that tiny microbes in the air were the cause.
- His swan-neck flask experiment in 1861 proved the microbes came from the air, not from the liquid, disproving spontaneous generation.
- From this he argued that germs also caused disease in humans, which is the germ theory.
Why germ theory was the turning point
- Germ theory gave, for the first time, a single testable explanation for infection, replacing centuries of guesswork.
- It meant scientists could now hunt for the exact microbe behind each disease, and it led on to vaccines, to antiseptics in surgery, and to better public health.
- Better microscopes made it possible to see the microbes and prove the theory.