I understand the basics of vaccines and I get the rabies vaccine works, but in the instance where you are attacked by a rabid animal and bitten, how does getting the vaccine immediately help with the development of the disease? Is it not already in your bloodstream?
In: Biology
Rabies attacks the nervous system itself. It does rather little in your blood. This means it often takes a long time for it to show symptoms as it spreads quite slowly towards the brain. Of course it depends where you got bitten in the first place…
This is somewhat good, as it means the time required for the vaccine to properly take effect still has a chance at helping fight the virus before it reaches the point where it’s irreversible and fatal.
Rabies is a *really* **really** bad disease. You wouldn’t wish it on your worst enemy. Every effort to fight it is worth it, because if you don’t get treated, you area *dead*, 100%. With proper treatment though, you’ll live. Please, do everything you’re instructed to do, to the letter.
Rabies is a fairly slow virus. So it takes a long time to spread and multiply throughout your body. The rabies vaccine have a much higher viral load then any animal bite. So you have a bit of live rabies virus in you and get a lot of rabies vaccine. This high viral load triggers your immune system to generate antibodies against the rabies. If you had the same viral load of live virus then it would have already been able to multiply faster then the immune system can kill it. But since the vaccine is unable to multiply the immune system destroys the vaccine and then continues to destroy the live virus while the viral load is low.
What rabies *does*, it’s “trick”, is it hides within your nerves. Your nerves are so armor coated nearly nothing, your own immune system included, can get past that armor. Rabies and a few other tricksy viruses *can* get past the armor and once they do, they are home free.
Between infection and getting inside your nerves, you have a window of time where your body can and does react to rabies and fight it, it just doesn’t typically do so fast enough to stop it from getting behind your nerve armor.
The first rabies vaccine was actually the first modern scientific vaccine and was created by Pasteur (the milk, wine, and beer guy) involved taking living rabies various and weaking it severely and then injecting it into your body progressively over several days. This was a big deal because Pasteur was fresh on heals of becoming famous for providing solid evidence for Germ Theory, the idea that microorganisms can have an impact on the macroscopic world. It was Pasteur for really blew the lid on germ theory with his work on wine and beer fermentation and his victory lap was producing an actual, deliberate, scientific vaccine to prevent a 100% fatal illness – rabies.
In his regimen each day you’d receive a slightly stronger shot of rabies until your finally just getting straight up injected with live rabies doses and your body has built up a full on immune reaction and just wipes out clean from your body.
With modern tech we’ve learned how to ‘kill’ (since viruses aren’t technically alive, you can’t really kill them so the term is used to mean “make it so they can’t infect you”) rabies viral particles so can just inject you with the “ID cards” of rabies so your body knows how to recognize it, without actually having the risk of actually becoming infected.
Fun Fact: When Pasteur developed his vaccine, he would suck the infectious saliva from dying dogs using a long metal straw and spit the saliva from the straw into flasks. His team kept a loaded revolver on hand during these sessions in case anyone accidently sucked the saliva into their mouths and infected themselves. Fortunately, they never needed to use them.
Fun Fact 2: What made Pasteur super special was that his previous work was on microscopic stuff you *could see* with a microscope. He proved these microscopic things could make us sick, spoil food, and ferment beer. BUT he *couldn’t* see viruses and he never did, we didn’t develop the tech for the for another century. But he figured there must be *something* in the saliva that made people get Rabies and it must be *like* a bacteria and he treated as such. He never actually saw the rabies virus, he just figured out *what it must be* and how to fight it.
You are correct that usually you need a vaccine *before* you are exposed to get much value out of it. Rabies is a bit of an exception to this.
Yes, a bite from a rabid animal will get rabies into your blood almost instantly. However, rabies doesn’t infect you through your blood, at least not directly. It travels through your nervous system and eventually enters your brain. Part of why it’s so deadly is that it’s able to cross what we call the blood-brain barrier. Almost nothing can do that, including medication and your own immune system. So once an infection is in your brain, it’s very very bad because, generally speaking, we don’t have any treatments for that and you don’t have an immune response either. You just die.
Rabies can sneak into the brain by traveling through your nervous system. The one break we have, is that this is a very slow process. Bloodborn pathogens will circulate through your entire body in a matter of minutes. If you get bit on the hand by a rabid dog it can take weeks or even months for the virus to make its way to your brain. That gives you plenty of time to go get the vaccine before the disease can infect your brain. As long as you get the immune response rolling *before* that, your body can clear it out and you’ll be fine.
If you wait, though, and don’t go to the doctor until you have symptoms, you’re dead. That’s too late for the vaccine because the virus is already in your brain. We don’t inoculate people ahead of time because it’s a painful and expensive shot that most people will never need it anyway. Plus you’d probably want a booster after a bite anyway and as I said there’s plenty of time to get it *after* a bite as long as people are educated about how to respond to an animal bite, which in America at least they generally are.
“Rabies Shots” are generally given as _post-exposure prophylaxis_, often abbreviated as _PEP_. _Post_ means after, and _prophylaxis_ is an action taken to prevent the development of disease.
So after an exposure or possible exposure to rabies, such as a bite from a wild animal known to harbor rabies, we give not one but two types of injections to help prevent the development of rabies.
One of these medicines is a vaccine, given in a series of 4 shots. Vaccines are medicines that train your immune system to be able to fight off an infection. As your post clearly notes, vaccines do not work immediately, and vaccines alone would not be sufficient to prevent rabies
The other medicine is what allows your body to fight off the infection immediately. It is called rabies immune globulin, or rabies Ig.
Immunoglobulins are proteins developed by the immune system. They are shaped like the letter “Y”, and the way that they work is the upper points of the “Y” are shaped to attach to disease-causing substances, and the lower part of the “Y” is like a beacon that tells the rest of the immune system where the problem is, so that it can come get rid of it
We get rabies Ig from the blood of people (or sometimes horses) that have received the rabies vaccine. Their immune systems have the Ig available so that when they are infected with rabies, their bodies can quickly find and neutralize it before they get sick
So we inject people with immune globulin – we try to get at least half of the injection close to the bite or wound to make it work better. This allows the body’s immune system to recognize and neutralize the rabies even though the vaccine has not yet started working. The Ig doesn’t last that long, but by the time it is gone, the vaccine has done its work and the body is producing it’s own Ig to continue to neutralize the rabies.
Rabies shots work the same as regular vaccines, rabies just needs the extra help to be noticed and attacked by the immune system before it does irreparable damage to the nervous system.
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