Edward Jenner was an English physician who lived in the 18th century, during a time when there was no good treatment or preventative measure against smallpox. The closest anyone got was a process called variolation, where one would be infected with a little bit of pus or breathed in powered smallpox scabs (gross), caught a less severe version of smallpox, and was then protected for life. This was dangerous because while the person was sick, he/she could spread the smallpox virus to others. With a mortality rate of 30%, this practice was dangerous and risky.
During trips out to the countryside to inoculate farm workers, Jenner and other physicians observed that those who had been infected with cowpox never showed smallpox symptoms. It was as if the smallpox virus had no effect on them. This did not hold true for all the workers though; some had been infected with the cowpox virus, yet still contracted smallpox. This inconsistency led many doctors to dismiss cowpox as a way to protect against smallpox. In his publication, Jenner wrote that these observations “damped but did not extinguish my ardour.”
Jenner continued to search for an explanation for the inconsistent protection. He realized that there were two issues. First, there were many pox-like diseases that humans can contract from a cow, yet all were called “Cowpox”. Second, in order to effectively inoculate a human, the cowpox virus must be collected from the cow at a specific time during the infection. Too early or too late during the course of the disease would mean that the cowpox had lost its “specific properties”, thus making it “incapable of producing that change upon the human frame”.
After overcoming these hurdles, the rest, as they say, is history. Edward Jenner successfully inoculated a boy with the cowpox virus from the hand of a milkmaid (she had recently been infected). The boy was then repeatedly exposed to smallpox and never got exhibited symptoms. Soon, hundreds followed suit. Cowpox was safer than variolation because the person would not spread smallpox after receiving the vaccine. Today, the vaccinia virus (of unknown origin but in the same pox family) is used to vaccinate against smallpox.
In 1980, smallpox was declared by the CDC to be fully eradicated. The only concern is that the virus could be used as a bioterrorism weapon; thus, military personnel are the only ones who still receive smallpox vaccines. For the rest of us civilians, it’s best not to forget what the world was like before vaccines. In fact, the word “vaccine” should be a reminder of its humble origins; it comes from the Latin root “vacca”, which means “cow”.