The history of eradicating smallpox involved an improbable team of, among others, a Buddhist nun, a cow, and an English physician (across generations and nations). Simona Zompi’s TED-Ed Lesson How we conquered the deadly smallpox virus walks us through the cinematic story, but what other additional fact about smallpox did Simona want to include in her lesson?

What’s your favorite fact about smallpox that didn’t make it into the TED-Ed Lesson?

Many more immunology-related lessons can be learned from the history of smallpox eradication. One of them is so-called herd immunity. In order to eradicate smallpox, mass vaccination campaigns were undertaken worldwide. In addition, systems were developed to detect and contain outbreaks. However, not 100% of the population needed to be vaccinated in order to achieve eradication. According to the concept of herd immunity, at least 80% of the population needed to be vaccinated. With diseases like smallpox that are passed from person to person, herd immunity makes it more difficult to transmit the disease when a certain number of the population is immune. For example, if person A is infected and person B is vaccinated, person B cannot get infected and thus would stop the transmission chain and would not be able to transmit the disease to person C who is not vaccinated. So, when a critical portion of the population is immunized, more of the community is protected.

To learn even more about smallpox, please visit Simona’s TED-Ed Lesson.