Let's talk for a moment about using vaccines to eradicate diseases. The first disease that was eradicated from humanity, and I think it's the only disease in humans, is the disease smallpox. We talked about smallpox in the beginning because it was such a horrible disease that it was one of the very first targeted for vaccination.
And then, of course, we know that people were using variolation, which is basically a... type of vaccination that puts live pathogenic virus into you, but hopefully you're able to overcome that without becoming seriously ill. Smallpox in the 18th century killed one out of every ten children.
We said that it killed on average about 30% of people who got infected the natural way. In the 20th century, which was not that long ago, the virus killed between 300 and 500 million people worldwide. And the problem with smallpox is that no effective treatment was ever developed.
So we were never able to find a way to actually treat people who've gotten sick, which left vaccination as the only method for prevention of this disease. And it is a horrible, horrible disease. Now, the thing about smallpox is that it infects only humans. So that's one advantage that we had with smallpox. Because there are no animal reservoirs, if you...
eliminate all transmission between humans, then there will be no humans that have this virus circulating and you've eliminated the disease. And so in 1967, the World Health Organization began an intensive worldwide vaccination program to try to eliminate smallpox. This was made a little bit easier by the fact that you can use ring vaccination in smallpox.
When someone gets smallpox, they get so sick that they usually can't spread it around much. So by the time they're contagious, you know they're ill already. Contrast this to COVID-19 right now, where we have asymptomatic people who don't realize they're sick, especially early in the infection and possibly even throughout their infection, they're able to transmit it. So smallpox was a horrible disease, but in a sense, it was easy because people got sick.
They didn't move around much. You were able to vaccinate all of their contacts and all of the people who become in contact with them. In 1977, the last...
naturally occurring smallpox case was identified in Somalia. And in 1980, the WHO, the World Health Organization, declared smallpox eradicated. So when I was a little kid, I was vaccinated for smallpox because smallpox was still circulating in the world.
But my kids have not been vaccinated for smallpox because there is no smallpox circulating in humans right now. So The World Health Organization has tackled a couple of diseases in addition to smallpox, with less success so far. One of the ones that they've tackled that looked like it was about to be eradicated was guinea worm. It used to be transmitted only by humans. It's now being transmitted by animals, and so that's made that a big challenge.
The other one that the World Health Organization is still working on actively is polio. Just to let you know how hard these problems can be, they started to try to eradicate polio in 1988. So this is another pathogen that is infectious only to humans, and human-to-human transmission is what we see. They were able to get the number of cases to drop tremendously.
So by 2001, we went from 300,000 cases a year to 483. So by 2001, there was very little polio in the world. And then this is where geopolitical conflict and public health end up fighting for predominance, I guess, in people's minds. So in Nigeria, where polio was still a problem, in 2003, the Molas that were there became very suspicious of the vaccination program.
And what happened is they discouraged people from vaccinating, the local vaccination effort broke down. polio cases tripled in Nigeria. So here we have our low at year 2000 and now we have in Nigeria over a thousand cases by 2006. And it was pretty dangerous to be a polio vaccination worker.
By 2007 in Pakistan it looked like polio was close to being eradicated. By 2009 the Taliban said no more administering vaccines. You might not remember, but in 2010, there was a huge flood in Pakistan that prevented a lot of the vaccine work that was being done.
So, of course, as soon as you stop vaccinating, this natural virus is there. It begins to multiply and a whole bunch more new infections. Then from 2010 on, we've seen... vaccination workers being murdered.
And of course, that's going to really be a problem because people aren't going to want to be the person out there administering vaccines if their lives are in jeopardy. And this has happened as recently as 2018. So it's really in this particular case, it's the geopolitical situations that have prevented polio from being eradicated so far. Now, this is just a little bit more global eradication. This is a little bit more up-to-date data.
So again, you're looking at the year 2000, we thought we'd had it licked. This is Pakistan. So you can see in 2014, there was a little blip, 2015. We talked about the fact that polio has been rising along with violence against vaccination workers. Here's Pakistan compared to other places that still struggle with polio.
So Somalia, Nigeria, et cetera. So it's still out. there and we're still working hard to solve this problem. Now in addition to the geopolitical issues and the challenge that I already mentioned that that smallpox was a much easier target.
This is data for 2017. I have not looked at data from this year but I will post updated data when I post this video as a link. I want to make a couple of points about the challenge with smallpox that are really nicely written here. Polio is spread by people who show no signs of being sick, so that's a big problem.
The poliovirus hides in and is spread through sewage. So remember, this is a fecal-to-oral transmittable pathogen. And this particular one, the other issue is something called the vaccine-type virus. And so in the vaccine-type virus...
you can, what happens with polio is you give people this oral polio vaccine, and it actually is good. It transmits mildly from person to person. When it transmits enough, and you end up getting to other people who haven't been vaccinated, sometimes it mutates, and those people can then become sensitive to a mutated form of the vaccine type virus. So they've been tracking issues with this vaccine type virus. The solution would be to revert to the injectable polio vaccine, but it's very difficult to administer.
Most of the places where you use oral polio vaccine, they don't keep vaccination records. They just vaccinate everyone in the village, and then they come back the next year, and they vaccinate everyone again in an attempt to just catch everybody. So it's not like people carry their little vaccine records around with them, and you'll know who got it and who didn't.
So this is a really hard problem to solve. The vaccine-type virus problem is interesting. So I have a video to show you that I'm going to post.
after this particular slide. This is another link that I will put up. In the fall of 2019, two of the three polio strains were eradicated, so they're just worried about this third strain, and again, they're primarily having issues with the vaccine-derived virus.
So there's a little bit more, and again, I'll put the link up for you to read more about it. All right, so the video will come after this slide. we'll have the vaccine-derived polio, the explanation of how that works is a really, it's very short, it's a very nice explanation.
And then we're going to move on and talk about different types of vaccine.