Variolation

Variolation, also known as inoculation, is the historical practice of inducing immunity to smallpox by deliberately exposing a healthy person to material from smallpox lesions. The aim is to trigger a controlled, milder infection that grants protection against future disease. Techniques varied: material was introduced to the skin via a small scratch or incision, or sometimes inhaled as powdered crusts from a smallpox pustule. While variolation reduced the risk of death compared with natural smallpox, it was not risk-free and could result in serious illness or transmission to contacts.

Evidence of variolation appears in East Asia and the Ottoman world before it reached Europe. The practice is often traced to China in the centuries before the 18th century, and similar methods were used in India and the Middle East. From there, travelers and scholars brought accounts to Europe in the 18th century.

In Britain and parts of continental Europe, variolation gradually gained acceptance after observations by physicians and diplomats who had encountered it in the Ottoman Empire. The most famous advocate was Lady Mary Wortley Montagu, who had her children variolated in 1721. Support grew despite concerns about safety and the contagiousness of variolating material, and some outbreaks prompted resistance.

Variolation remained common through the 18th and early 19th centuries, but it carried risks of complications and transmission. The development of vaccination by Edward Jenner in 1796, using cowpox material to confer immunity, offered a safer alternative. Vaccination gradually supplanted variolation in most countries, contributing to the eventual eradication of smallpox in the late 20th century. Today variolation is mostly discussed as a historical precursor to modern vaccination and immunology.