Thread by @kakape

I suspect we can all use a tiny break from refreshing our browsers and since we’re thinking a lot about vaccines and vaccine delivery these days, let me share sth with you that I learnt recently about the world’s first vaccine, the smallpox vaccine and that kind of blew my mind.

Many of you know the story of Edward Jenner. In 1796 he took some liquid from a cowpox blister and scratched it into the arm of eight-year old James Phipps. Jenner later inoculated the boy with smallpox and Phipps did not get sick. This is usually seen as the first vaccination.

The reality is a bit more complicated. (For one it was probably horsepox not cowpox that Jenner used.) But that’s not the point. It’s how do you get from that one vaccination to vaccinating millions of people given that cowpox/horsepox was actually quite rare?

Keep in mind: People did not know how vaccination works or that this was a virus at work (it was almost a century before viruses would even be discovered). So people didn’t know what to preserve or how to do it and there wasn’t a global supply chain anyway.

So how do you do it? Well, mostly you do it by using children as incubators: You vaccinate a child, wait until it develops a pustule and then use material from that pustule to vaccinate the next child. That is how the virus/vaccine spread from one place to the next in Europe.

Take France as an example: “The best way of getting hold of some fresh cowpox was finding out that someone in Paris was vaccinating fairly regularly”, Michael Bennett from @UTAS_ told me. (You can read more about all this in his excellent book “War Against Smallpox”.)

“If you’re a surgeon from Lyon... you’d go to Paris with your daughter, you'd have your daughter vaccinated and then by the time you got back to Lyon, your daughter's vaccine pustule would then set you up in business because you could then use that vaccine to start inoculating”

Of course this meant you needed a continuous stream of children to be vaccinated. And one way that doctors did this was to vaccinate poor people for free to keep the virus going and then charge the rich people for their vaccinations.

So that’s how vaccination “travelled” on land. And how did you get the virus from Europe to the Americas for instance? More children and what Bennett calls “some extraordinary vaccine expeditions”:

“They would actually take groups of children and vaccinate them two at a time every every week. So you vaccinate the first two, and then from them, you vaccinate to others and vaccinate to others. And this is how they took vaccine live to from Spain to Latin America in 1804"

And that’s how smallpox vaccination first spread around the world. As Bennett told me: “All the vaccine in the world really came from England, but through this process of what I call arm to arm”.

Not sure there are any big lessons here, except maybe that having a vaccine is not enough, you need to actually deliver it to people as well and that can be challenging. We will be talking about that soon with Covid19 vaccines as well (plus vaccine confidence).

Plus: the history of medicine is fascinating and I feel like we should all have learnt way more about it in school. If you speak German, this latest episode of @pandemiapodcast is here (quotes are in the original though):

viertausendhertz.de/pan14/

This is the book by Michael Bennett: cambridge.org/es/academic/su…

And here’s a ahort paper on one of these vaccination expeditions, led by Francisco Xavier de Balmis h/t @scopedbylarry academic.oup.com/cid/article/41…

“In order to preserve the vaccine during the journey, the decision was made to bring 22 orphaned children from La Coruña, 18 of whom were from the charity hospital and the other 4 of whom were from La Coruña Orphanage”