eli5 Why small pox inoculation is any different from catching it naturally?

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So I’m having trouble with this, and I’ve went through different links on Google and can’t find an answer. So they would poke into sores of people who had smallpox and then proceed to cut the patient and insert the infection directly into them. I’m not understanding why catching small pox that way would be any different than catching it naturally?

I am specifically referring to how it was done during the revolutionary war, not today’s vaccines. But wouldn’t mind knowing how those two things differ as a bonus

In: Biology

11 Answers

Anonymous 0 Comments

[Kurzgesagt has a great video about smallpox](https://www.youtube.com/watch?v=Kr57ax0OWMk), definitely worth your time if you’re curious about the disease. I think they even touch on the question you’re asking.

The gist of it was that typical smallpox infections start in the throat when you inhale droplets containing the virus. The virus is specialized for that kind of transmission, so infections starting in the throat are very deadly. Inoculations introduce the virus into a part of the body that it isn’t specialized for, which gives your immune system a much better chance of fighting back against it before the disease can really take hold

Anonymous 0 Comments

In natural infection smallpox would be breathed in, hit all the internal organs and multiply first, and only then appear on the skin.

Stabbing it into skin causes immune reaction to begin immediately in response to damage, which catches the virus at the early stage and doesn’t let it multiply so much.

The way it was done was still not entirely safe and sometimes led to severe disease and even death in 1% cases, which admittedly was a big improvement compared to getting smallpox that led to death in about 20% cases.

It was then replaced with infecting with related but way less dangerous cowpox virus, and then to another related virus vaccinia.

Anonymous 0 Comments

Great responses, but I always love pointing out that Edward Jenner’s work with Cow Pox is what gave us the word “vaccination” from the Latin root Vacca meaning “cow”. Thus getting vaccinated is to be Medically Cowed.

Anonymous 0 Comments

This is called variolation.

In china and asia, for example, they would grind scabs of _mildly infected individuals_ and snort them. This was the first variolation. Another method was the one you mention, but the aim was the same: this normally meant the body was exposed to damaged/weakened forms of the virus, or at least a milder strain, which would give immunity without as high a risk of death. However, there was little control, and often the resulting infection was still lethal, and no different from contracting the full blown disease.

Edward Jenner was arguably the first to try the safer vaccination – where a completely different, but similar virus was used to infect someone. Cow pox was different enough to ensure high survival rates, but similar enough to smallpox that people became immune to both.

Anonymous 0 Comments

So for smallpox – there’s multiple versions, or “strains”, of the virus, and they’re not all equally deadly. Some varieties had a mortality rate of like 30% while others had a mortality rate of like 1%. But their antigens are similar enough that if you gain immunity to one, you gain immunity to the others.

Yes, you’re still getting live virii (in the original innoculation procedure, anyway) and purposely getting yourself sick, but the point is you’re trying to purposely pick the *least bad* strain of the virus to put up with. If someone is known to have suffered from smallpox in the past and survived, there’s a good chance it’s because they caught the less deadly strain. It’s technically still a gamble – they could be one of the 70% that survived the bad strain – but it’s still *better* odds than gambling on whatever you happen to pick up naturally.

> But wouldn’t mind knowing how those two things differ as a bonus

There’s a lot of kinds of vaccines that work slightly differently. But in general, even though a virus doesn’t have that many parts, they do need to all be there and working for a virus to be infectious. Generally that’s a membrane like cells have, proteins on the surface of the membrane (“spike” proteins) that screw with proteins on the outside of victim cells, and the genetic information that codes for the spike proteins. So most vaccines usually include *some, but not all* of the parts the virus is composed of – enough to make your immune system freak out and start pumping out antibodies, but not enough to actually *do* anything per se.

Like the COVID vaccine was an mRNA vaccine, meaning it just includes the virus’ genetic information, but not the virus itself. That genetic information can get into cells where the ribosomes will transcribe it to produce the spike proteins. Oh shit, there’s spike proteins in the body, that raises the immune system alarms and its starts trying to find an antibody to counter them. But the spike proteins *alone* can’t really do anything unless they’re part of the whole viral package with a genetic payload and a membrane to hold it. So it can’t keep infecting new cells.

Anonymous 0 Comments

The virus in the vaccine is not, never has been, the smallpox virus. It is derived from the Cowpox virus which never was the devastating disease that smallpox was.

Read up on [Edward Jenner](https://en.wikipedia.org/wiki/Edward_Jenner)

Anonymous 0 Comments

The inoculation comes from a person who has already recovered from the disease, so it comes with antibodies that already know how to fight the disease. It’s the difference in-between getting Ikea furniture or LEGO with the instructions for assembly or just having to figure how all the pieces go together yourself. Having instructions speeds the process and allows the body to build its immunity much faster, preventing the disease from getting deeply rooted into the body’s systems.

Anonymous 0 Comments

Others have described the difference. What you are describing is called variolization. Exactly where this practice developed is unclear but one of the earliest written accounts was from [Lady Mary Montagu](https://time.com/5542895/mary-montagu-smallpox/), a smallpox survivor, whose husband was sent to be the English ambassador to Turkey.

She described how she had her children variolated. They became sick eight days later (it’s almost always exactly eight days) and then quickly recovered. After this, they never got smallpox.

Variolization led to mild disease and protective immunity in ~99% of cases. ~1% developed smallpox. But against an excruciating, permanently mutilating disease with a ~50% mortality rate, the practice became popular.

It would be almost a century until Edward Jenner would attempt the practice with cowpox (or what he thought was cowpox; it turns out vaccinia has 99.7% sequence identity to horsepox). With vaccinia, the efficacy against symptomatic smallpox is ~90% and those few breakthrough cases were mild with a high rate of survival and only minimal scarring. Less than 1 in 100,000 people develop disseminated vaccinia (which is usually fatal). This is why it’s only used in military personnel and people who work with orthopoxviruses.

We have a newer one now called JYNNEOS. It uses a virus called Modified Vaccinia Ankara (MVA). This was created by taking a vaccinia strain (presumably isolated in Ankara) and passaging it on chicken eggs for hundreds of times. The resulting virus lost 20% of its genome and cannot replicate in mammal cells. So it gets into cells, makes a bunch of vaccinia surface proteins, and then goes nowhere. It’s the version that was used against monkeypox most recently with ~90% efficacy.

Anonymous 0 Comments

Well, firstly, smallpox itself wasn’t used for inoculation. Cowpox was used, which was a similar virus.

It’s a lot less spread around now, but there used to be a notable amount of pretty milkmaids- not because they were selected because they were pretty, but because they rarely developed smallpox.

The guy who invented the original smallpox vaccine noted that milkmaids didn’t get smallpox- but all those milkmaids, who often milked the cows themselves, had scarred-up *hands*, because they got cowpox, a similar but MUCH less severe and deadly disease, from milking. Cleaning standards were also higher where milk was worked with because dairy products can develop off flavors if exposed to things like smoke, so the equipment would’ve been washed with proper soaps and scalded with boiling water more often, which caused chapped hands.

So the milkmaids got cowpox infections around places where their hands split from being dry and callused. So when Dr Jenner started trying to vaccinate people, he’d use cowpox and create a little lesion, effectively giving the person a cowpox infection.

Anonymous 0 Comments

First off the vaccine isn’t smallpox, but a virus called vaccinia. To our immune system it is close enough to smallpox that you will be immune to smallpox

Generally speaking, this vaccine only causes a localized lesion along with feeling bad for a couple of days.

Small pox will, at best, cause massive scarring. It can cause blindness and other horrible issues. Smallpox will kill up to 30% of people who catch it.