Types of Vaccination, Toxoid Sabin MMR DPT Conjugated Killed Attenuated vaccine salk rabies

distinguished future physicians welcome

to stomp on step 1 the only free video

series that helps you study more

efficiently by focusing on the highest

yield material this is the seventh video

in the playlist covering all of

inflammation and immunology if you

missed the previous videos in the

section you can click on the stop on

step one logo here to be taken to a list

of the available videos in the playlist

this specific video is going to cover

the various types of vaccines the

mechanisms by which they work and give

examples of each type so we're going to

be talking about things like conjugated

vaccines killed inactivated vaccines

live attenuated and passive immunization

we will start with passive immunization

which you can see here in the top right

corner I only give a high yield rating

of one on a scale from 1 to 10 so it's

not super important for step one but I

will take a second to discuss it here

passive immunization involves delivering

preformed antibodies to the individual

at risk of infection you're taking a

humoral immunity from one an individual

or animal and transferring it to another

individual who's at risk it has an

instant effect as the immunoglobulins

are preformed and the body doesn't need

to waste any time trying to figure out

how to make antibodies of it boom that

are targeted at the pathogen however

passive immunity has a short duration of

action because it only works for the

lifespan of the transferred antibodies

which is usually about a few weeks there

are natural examples of passive immunity

specifically with infants the breast

milk has IgA that is transferred from

the mother to the infant to give them

you costal immunity similarly IgG is

transferred from the mother to the fetus

through the placenta through these

mechanisms an infant that does not yet

have a mature immune system can be

protected from pathogens purified and

antibodies made from horses are also

treatment options for tetanus botulism

and rabies so

you expose a horse to whatever happened

in trying to treat for you take that out

of their blood and purify it and you can

give to humans as a way to treat and in

most cases you're using this treatment

after a person is exposed to the

pathogen so this is sort of a last

minute thing once you realize somebody's

already starting so some signs of one of

these diseases you give them this

passive immunization because it works

really quickly following an infection

with one of these organisms a

traditional or active immunization is

not an option because it takes too long

to start and the patient could die by

then now we can discuss active

immunization which is the focus of

mostly immunization questions in fact

anytime you're not specifically talking

about an example of passive immunity you

can just assume they're talking about

active immunity which involves helping

the hosts make their own antibodies

against the pathogen of interest it

takes longer to start working than

passive immunity but its effects are

more potent and can last for much longer

many many years in fact instead of weeks

the rest of this video is going to cover

different types and mechanisms of active

immunization through the activation of

the adaptive immune system our bodies

have immunologic memory which allows us

to react much faster and with the higher

potency the second time we see a

particular antigen this works really

well for relatively benign pathogens for

example if you get a cold once then your

immune system will be better at fighting

the causative pathogen the next time

it's exposed to it

however this trial-by-fire method

doesn't work well for infections that

have significant morbidity and mortality

we need a prophylactic way to prime

immune system and prevent the initial

infection from causing problems

vaccinations or immunizations are the

way we gain immunologic memory without

having an active infection this involves

exposing the patient to an antigen on

the pathogen of interest in a way that

is not dangerous this dress rehearsal

lets the immune system sort of practice

fighting the pathogen in a situation

where the patient isn't actually

infected after being exposed to the


present in the vaccine the patient will

react much faster with greater potency

if they ever actually see the real

pathogen one type of active immunization

is a live or attenuated vaccine it

involves giving the patient a small

amount of the living pathogen you are

trying to immunize for which will

initially seem counterproductive if

you're trying to prevent a pathogen why

would you give that pathogen somebody

else and that's where the process of

attenuation comes in attenuation is the

process of altering a pathogen to

diminish its virulence for example you

can take a pathogen and grow it outside

of the human OHS for many many

generations so adapts to a nonhuman

environment when you take that pathogen

and put it back in a human it no longer

has the adaptions it used to thrive in a

human environment these attenuated

pathogens can grow inside of a patient

but they grow very slowly and they have

lost their ability to cause disease

these attenuated pathogens although

they've lost some adaptions look very

similar to infectious pathogens that

cause the actual disease so the immune

response against the attenuated pathogen

will work against the real pathogen

should the host ever become exposed to


the immunologic memory induced can last

for decades with live attenuated

vaccines meaning that you don't need

booster shots as much as some other

vaccine types we're going to talk about

later the immune response to live

attenuated vaccines is also very strong

it's because the live pathogen can

induce more types of immune response

including humoral immunity mainly IgG

you go sole immunity IgA and even some

cell mediated immunity however there's

one big drawback to the live attenuated

vaccines and that's because you're

giving a live pathogen there's a chance

that through mutations or adaptions that

live pathogen can revert back to the

infectious form it is extremely rare but

it's possible that this attenuated virus

or bacteria can go back to the original


and cause the disease here's a list of

the most important examples of this type

of vaccine for the USMLE step 1 exam the

MMR vaccine treats for measles mumps and

rubella and those are examples of Lie

attenuated vaccines

there's the Sabin vaccine pronounced

like Nick Sabin but spelled a little bit

different that's going to be for polio

and this is the oral form it's not used

in the u.s. much anymore because the

mutation issues where it can very rarely

cause polio in person you're back tuning

but it's still used in some third-world

countries because it can be given orally

and therefore is a lot easier to

distribute even if you've got poor or

healthcare infrastructure and there's

also the varicella zoster vaccine or the

chickenpox vaccine the other major class

of vaccinations that were to talk about

involves giving a patient a pathogen

that has been killed with heat or

formaldehyde now if we're talking about

viruses you can't really kill a virus

because all of them alive but it's still

fits and it's easier to understand it

that way

these dead pathogens still have surface

antigens that are recognized by the

immune system creating an immune

response however compared to the live

attenuated vaccines be killed and

activated vaccines have a relatively

weak response and the response is much

shorter term it's not going to last for

decades it's going to more last for

years meaning you may need some booster

shots and well IgG is generated against

these pathogens you're generally not

going to have any postal immunity or

cell mediated immunity which is why the

potency is lower the question is if it

doesn't last as long as it's not as

strong why would you ever use this type

of vaccine and the big caveat is that it

can't cause the infection the live

vaccines can mutate back into the actual

pathogen but since these pathogens

aren't alive they can't do that so you

have almost no risk with this if the

vaccine was prepared correct

going here are the most important

examples of this type of vaccine you'll

have the Salk vaccine which is also for

polio like Sabin but this is the

injected type is the one that's more

commonly used now you'll have the rabies

vaccine and the pertussis vaccine there

are versions of the influenza vaccine

which are killed and activated but

there's also other types of the

influenza virus vaccines that don't

include full dead pathogens they include

just fragments of the pathogen a toxoid

is a bacterial exotoxin that has been

inactivated with heat or formaldehyde so

it's the same way that an inactivated

killed vaccine would kill the full

pathogen it's just now you're treating

just the toxin and not the whole

pathogen this heat or formaldehyde

removes the toxic effects of the toxin

so that it can be given in a vaccine

without causing the disease this type of

immunization creates immunologic memory

against the noxious toxin instead of the

pathogen itself which is relatively

innocuous toxoid vaccines are available

for tetanus and diphtheria the DPT

vaccine or Tdap is going to have toxoid

vaccines against diphtheria and tetanus

in it as well as a pertussis vaccine

that is not a toxoid toxoids are

proteins that are highly immunogenic and

that fact can be used to our advantage

for other types of vaccines called

conjugated vaccines the reason toxoids

are so immuno genic

is because their proteins and proteins

can activate T cell dependent immunity

on life carbohydrates what we do is we

covalently bond a carbohydrate antigen

to a toxoid to create vaccines that work

better a carbohydrate such as a fragment

of a bacterial carbohydrate capsule is

not immunogenic enough to create a

strong immunologic memory and an

effective vaccine but if you connect a

carbohydrate antigen to a protein toxoid


T cell dependent portions of the

adaptive immune system will be able to

recognize it better this method of

combining a carbohydrate immunogen with

a carrier toxoid protein is referred to

it as conjugate vaccine using this

method you can create vaccines against

the polysaccharide capsules of bacteria

like type B H flu and Neisseria

meningitidis that is all I have about

vaccines now I'd like to take a quick

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it will cover the different types of

immunodeficiency thank you so much for

watching and good luck with the rest of

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