Smallpox vaccine: the story on HearLore

Smallpox vaccine

In 1796, a farmer's daughter named Sarah Nelmes contracted cowpox, a mild disease that left her with pustules on her hands, but it was her infection that would eventually save millions of lives. Edward Jenner, a country doctor in Berkeley, England, observed that milkmaids who had contracted cowpox never seemed to catch smallpox, the deadly disease that killed up to 35% of those infected. He decided to test this observation by taking fluid from one of the milkmaid's sores and injecting it into the arm of an eight-year-old boy named James Phipps. Weeks later, Jenner deliberately exposed the boy to smallpox, and the child remained healthy. This single experiment, performed on the 14th of May 1796, marked the birth of vaccination, a term derived from the Latin word vacca, meaning cow. Before this moment, the only way to induce immunity was variolation, a dangerous practice of deliberately infecting people with actual smallpox scabs, which carried a mortality rate of 0.5 to 2 percent. Jenner's method was revolutionary because it used a related but much milder virus to build a shield against the killer, proving that immunity could be engineered rather than risked through infection.

The Arm To Arm Struggle

For the first century of its existence, the smallpox vaccine was a fragile, living substance that traveled from person to person, creating a chain of infection that was as dangerous as the disease it prevented. From 1796 until the 1880s, the vaccine was transmitted through arm-to-arm vaccination, where lymph fluid was scraped from the pustule of a vaccinated child and transferred directly to the next recipient. This method allowed the virus to remain potent but introduced a terrifying risk: the vaccine itself could carry other deadly diseases like syphilis, tuberculosis, and tetanus. Historical records estimate that out of 100 million vaccinations, approximately 750 cases of syphilis were transmitted through this process. The practice was so prevalent that in 1896, the British Government Vaccine Establishment began issuing glycerinated calf lymph to replace the human-to-human transfer, yet the crude starting material scraped from animal skin remained heavily contaminated with bacteria. It was not until the late 1940s that Leslie Collier, an English microbiologist, developed a freeze-dried method that allowed the vaccine to survive without refrigeration, making it possible to transport the virus to remote tropical areas where the cold chain was impossible to maintain. This technological leap was essential for the global eradication campaign that would follow, but for decades, the vaccine was a double-edged sword that could kill as easily as it saved.

The Bifurcated Needle

Common questions

When did Edward Jenner perform the first smallpox vaccine experiment on James Phipps?

Edward Jenner performed the first smallpox vaccine experiment on James Phipps on the 14th of May 1796. This single experiment marked the birth of vaccination and proved that immunity could be engineered rather than risked through infection.

What was the mortality rate of variolation before Edward Jenner developed the smallpox vaccine?

Variolation carried a mortality rate of 0.5 to 2 percent before Edward Jenner developed the smallpox vaccine. This dangerous practice involved deliberately infecting people with actual smallpox scabs to induce immunity.

How did the British Government Vaccine Establishment change smallpox vaccine distribution in 1896?

The British Government Vaccine Establishment began issuing glycerinated calf lymph in 1896 to replace human-to-human transfer. This change aimed to reduce the risk of transmitting other deadly diseases like syphilis, tuberculosis, and tetanus through the vaccine.

When was smallpox officially declared eradicated by the World Health Organization?

Smallpox was officially declared eradicated in 1980 after the last endemic case was recorded in Somalia in 1977. This achievement made smallpox the only human disease to be completely wiped from the face of the earth.

Which vaccine did the United States order over 200 million doses of between 1999 and 2001?

The United States ordered over 200 million doses of ACAM2000, a second-generation vaccine, between 1999 and 2001. This stockpile was built to guard against the possibility of bioterrorism following the September 11 attacks in 2001.

What virus is the closest relative to the vaccinia strains used in modern smallpox vaccines?

Modern science suggests that the horsepox virus is the closest relative to the vaccinia strains used in modern smallpox vaccines. Whole-genome sequencing in the 1990s and 2000s revealed that some 19th-century vaccines were 99.7% similar to horsepox.