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Passage: The history of vaccination

The history of vaccination

A. The concept of inducing immunity through deliberate exposure to a pathogen predates modern medicine by centuries. In 18th-century China and the Ottoman Empire, a practice known as variolation was widespread: material from the pustules of mild smallpox cases was introduced into the skin of healthy individuals, producing a milder form of the disease and — in most cases — subsequent immunity. The practice carried significant risk: approximately 1–2% of those variolated died as a result, compared with a 20–30% fatality rate from naturally acquired smallpox.

B. The modern era of vaccination began with Edward Jenner's 1796 observation that milkmaids who had contracted cowpox appeared to be immune to smallpox. Jenner inoculated an eight-year-old boy with cowpox material and then exposed him to smallpox — a procedure that today would be considered deeply unethical. The boy did not develop the disease. Jenner published his findings in 1798, coining the term 'vaccination' from the Latin 'vacca' (cow). His work was initially met with considerable scepticism from the medical establishment, who were unconvinced by evidence drawn from a single case.

C. The germ theory of disease — the understanding that specific microorganisms cause specific illnesses — transformed vaccine science in the 19th century. Louis Pasteur demonstrated that artificially weakened (attenuated) forms of a pathogen could confer immunity without causing serious disease. This principle — the attenuation approach — underpins many vaccines used today, including those for measles, mumps, and rubella. Pasteur's development of the rabies vaccine in 1885 represented a landmark application of this methodology.

D. The 20th century saw vaccination scaled from individual protection to population-level disease control. Mass immunisation campaigns against polio, diphtheria, and measles dramatically reduced the incidence of these diseases in high-income countries within decades. The global eradication of smallpox, certified by the World Health Organization in 1980, remains the only human disease to have been eliminated through vaccination — a feat that required coordinated efforts across more than 30 countries and the vaccination of over 500 million people in a single decade.

E. Contemporary vaccine development has been fundamentally altered by molecular biology. Recombinant DNA technology allows scientists to identify specific proteins on a pathogen's surface and produce them artificially, stimulating an immune response without introducing any live or killed pathogen. The mRNA vaccines developed for COVID-19 represent a further evolution: rather than introducing a protein, they instruct the body's own cells to produce it temporarily. The development of effective mRNA vaccines in under a year broke previous records by a wide margin, though critics noted that the compressed timeline was made possible partly by unprecedented levels of regulatory and financial support.