If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:10:56

Video transcript

so recently I got into a conversation about the world's greatest medical achievements and we were wondering we were trying to think what is the world's greatest medical achievement and after some long thigh you know I was putting some some deep thought into it I came to the realization that vaccinations are kind of an astounding medical achievement in fact maybe even the world's greatest medical achievement and I think antibiotics come very close and the reason it's such a great medical achievement is because with vaccines and antibiotics as well there's the potential to completely wipe out a disease that affects humans completely eradicated and we've come kind of close with polio polio is effectively eradicated from the Western Hemisphere of the world and it's all thanks to vaccinations and immunizations unfortunately it still exists in some recesses some corners of the world but I think it's very cool that we've come very close so I want to dive deeper into how these vaccinations work and for polio there are really two major types of the vaccination there were two major vaccinations that were created there's the Sobhan vaccine so the zabun form and there's also the other form which is known as sulk so the Czaban polio vaccine and the Salk polio vaccination so what's the difference between these two so the Sobhan vaccine is actually considered it's alive but attenuated vaccine and attenuated just means decrease in affectivity so the vaccine itself is actually effective with three doses of the vaccine it has about a 95% effectivity so it's 95% efficacious so attenuated just really refers to the virus itself so in this vaccine the virus is actually alive but it's no longer virulent the scientists that created this vaccine removed the ability for the virus to cause damage to the cells of our body so the virus cannot cause damaged body anymore now the Salk vaccine on the other hand is a killed form of the virus so it can even replicate it's just completely dead and this is also a very efficacious vaccination so with only one dose it's about 90% efficacious and after three doses it's 99% efficacious so it's a very effective vaccination and the other major difference between these two is the Sobhan vaccine is a liquid medication so it comes in a bottle of liquid and you can drink it whereas the Salk vaccine is injected so it's considered intramuscular injected into the muscle through a needle through a syringe so already you can see a lot of differences between these two but you know what are the advantages or disadvantages of either of these let's dive a little bit deeper the benefit of the Sobhan vaccination is it induces both humoral as well as cell mediated immunity whereas the Salk vaccine really only induces humoral immunity so there's no cell mediated immunity with the Salk vaccination so what does that even mean so what does that mean what is humoral vs. cell mediated immunity well first let's take a look at humoral so let's take a look at a bunch of cells of the body so here are a bunch of cells of our body and let's say the nasty virus the polio virus which is this little green guy in here gets into the body now it's floating around in the interstitial fluid so it's floating around in the body it's looking for cells to infect right now remember viruses get inside cells and then replicate so create more copies of themselves and then they burst out all these new copies so in our body we have certain white blood cells and responsible for the humoral immunity are these white blood cells called B cells and B cells are kind of cool they're actually among my favorite cells they create what are called antibodies right and these antibodies are these little wide shape proteins that end up finding something they recognized and attach to it so when your body is exposed to the polio virus some B cells of the body will recognize this virus right they'll recognize it and they'll create antibodies that will bind to it and this alerts the b-cells that there's something wrong and they call out to other reinforcements other cells of body and these reinforcements come and help wipe out the virus so the reinforcements come in and knock out all these viruses so that's great however the major problem is that once the virus gets inside of a cell the B cell can no longer do anything so a B cell comes along sees the cell and thinks oh there's nothing wrong and then continues on its merry way so it doesn't do anything so that's the problem with humoral immunity once the cell is infected there's no way for B cell to get to it now with cell mediated immunity so we'll draw the cells of the body again and let's say we've already been infected right and for good measure let's let's put another normal cell over here so B cells can't get these guys but there's other white blood cells of the body known as T cells and T cells are specialized at recognizing when a cell is sick so when another saw the body is sick these cells actually send a distress signal to the T cell and say hey come over here I'm sick you need to help me out now unfortunately because they're already infected there's nothing these T cells can do except make sure that they eliminate the threat so they kill off these cells and so that cell mediated immunity from cell to cell so the Sobhan vaccine creates greater immunity because it induces both humoral and cell mediated immunity whereas the Salk only induces this humoral immunity over here now the Sobhan vaccine is also very cheap it's not too costly whereas creating an injectable vaccination is more costly than this oral dose and another great thing about the saben vaccine is the immunity can actually be passed from person to person so let's draw some people here and you'll see if we take this virus right this is the live attenuated form of the virus and we give it to this person it still replicates so it actually it's an int arrow virus right it replicates in the intestines but also in the throat too so it replicates in this person and can be passed on to these other people now the beauty of this is since this virus is not virulent right like it's attenuated it can't do any damage it gets passed on and confers immunity to these other people so they get the immunity whereas with the Salk vaccination the virus in this vaccine are dead so we provide immunity to this person right we'll create this little bubble around them so they're immune but they can't pass it on so the immunity it stops right there and going back over here right these guys are immune right they receive the immunity when the virus is passed on to them so from a population health standpoint you can reach a larger number of people using this saben vaccine versus the Salk vaccine so in areas where it's very challenging very difficult to reach people the oral vaccination form is used however in places like the United States where it's often required to get a vaccination it's much easier to locate people and provide them with immunity so now looking at these two it seems like the savin form of the vaccination is much better than the Salk form oh and before I continue I should shown you this a little bit earlier you can remember the names of these vaccinations by looking at the letter so Salk has a K that's the killed form of the vaccine whereas Sobhan has an N and that's the attenuated form of the vaccination so that can help with remembering which is which so now going back and looking at these it looks like the saben form is more advantageous there's more advantages however it's not without its disadvantages the two major disadvantages that I see with the saben vaccine is if there's another entero virus so polio is an entero virus and some examples include the Rhino virus echo virus Coxsackie virus all these are enteroviruses if an entero virus happens to affect this person at the same time as they're getting this oral form of the vaccine this other virus can interfere with the immunity so the immune system so let's say this other internal virus is in here replicating the immune system doesn't know that the vaccine introduced Joost is not dangerous and so it tries to fight both of these off and can get overwhelmed and a person may not gain immunity from the polio virus and in parts of the world where there isn't proper health care this can be a huge problem because individuals might be afflicted by other viruses at the same time so you have to really think about this and another major issue is very rarely and you know I want to put the numbers down here one in 2.5 million people that receive the live form of vaccination can sometimes have something where one of the live viruses may transform and become virulent this is a very small number and a very small risk but it's still a risk and if this virulent strain now takes over it can infect the patient and they can contract polio so because of this never never never never give the live vaccine to somebody who is immuno compromised so if somehow their immune system is not functioning properly this gives the virus more time to revert to this virulent strain so never give the live vaccine to somebody who has an ineffective immune system and this is the same reason you never give the oral vaccine to an infant younger than one year old and also pregnant women and really anybody who has a close contact to people of this demographic so you don't want to give it to a mother who has a one-year-old child either or to somebody who lives with their very elderly sick grandparent or something like that however again from a population standpoint this can be very effective at reaching a larger number of people much more quickly so in summary it's important to understand the differences between these two so that you can know the advantages and disadvantages of using either one