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  • This episode of SciShow is supported by Brilliant!

  • You can learn more at Brilliant.org/SciShow.

  • {♫Intro♫}

  • Okay, so hopefully it's not too shocking to hear that the measles vaccine saves lives.

  • Before widespread measles vaccinations were a thing, the measles virus caused over four

  • million deaths a year.

  • Thankfully, since measles vaccines started making their rounds more than fifty years

  • ago, there's been a decline in childhood mortality.

  • A massive decline, in fact.

  • Deaths of children have dropped by up to ninety percent in lower income countries.

  • And that's…a lot more than you'd expect if the measles vaccine just prevented deaths

  • from the disease itself.

  • Turns out vaccinated kids are also not dying from other illnesses that occur as secondary

  • infections or within a few years.

  • And that's because measles messes with your immune system in a unique way, leaving you

  • susceptible to illnesses you were previously immune to.

  • Yeah, the measles virus is /that/ nasty.

  • Your immune system works really hard to keep you protected from illnesses.

  • And one way it does that is with your adaptive immune systembasically, a whole army of

  • cells that can learn from pathogens.

  • Among the most important weapons in the adaptive

  • immune system are lymphocytes, special white blood cells that can remember what's tried

  • to take you down before, so next time it comes around, your body is ready.

  • T cells are a type of lymphocyte, for example, and they have the essential task of finding

  • unhealthy or infected cells and destroying them.

  • There are also B cells, which bind to intruders, and alongside T cells, help create antibodies

  • during an infection.

  • And while they're fighting what ails you, B and T cells also create memory cells.

  • These are clones of the specific B and T cells which successfully bound to the pathogen.

  • And they remain after an infection holding onto information about each threat the body

  • has been exposed to.

  • Basically, they create an immune system memory bank of the bad guys you've battled off.

  • We know from studies in both macaque monkeys and humans that the measles virus attacks

  • and kills B and T lymphocytes.

  • So it might literally wipe out part or all of your immune system's memory bank.

  • And although white blood cell counts in your blood return to normal levels after a few

  • weeks, it's likely these replacement B and T lymphocytes are measles-specific.

  • So your immune system might successfully beat the measles virus and create a life-long immunity

  • to it, but it could also stop remembering a lot of what it knew beforehand.

  • Initially, it was thought that this immune amnesia effect only lasted for the weeks immediately

  • following infection.

  • And that might make sense if the virus doesn't wipe out your entire clone army.

  • But a growing body of research suggests it lasts way longer than that.

  • Data on childhood health that's been collected worldwide since measles vaccines first became

  • widespread suggest the virus disables immune memory for two to three years.

  • In one study, researchers looked at the medical history of over two thousand measles patients

  • compared to children who never caught the measles.

  • Their work showed that children who once had measles were diagnosed with more infections

  • and were given more anti-infection prescriptions than the measles-free population for up to

  • five years after recovering from the measles.

  • To put it not-so-lightly, someone who survives a bout of measles could become infected with

  • a life-threatening disease years later that they would have otherwise fought off easily.

  • Scientists are still trying to figure out the exact mechanisms for this.

  • Some studies suggest the live measles vaccine itself helps by directly enhancing your immune response.

  • You see, in addition to B and T cells that take on intruders and remember past wrongs,

  • there are other immune cells which use nonspecific defenses against foreign cells in the body

  • The measles vaccine might make these innate immune cells more responsive when they reencounter

  • familiar pathogens in a way that's totally unrelated to antibodiessomething referred

  • to as trained immunity.

  • But other research suggests that measles vaccines simply prevent the immune amnesia effect from

  • happening.

  • You know, by stopping the measles infection in the first place, and therefore, preventing

  • it from killing off your memory cells.

  • There are other questions about all this, toolike, how much immune memory is erased

  • by the virus.

  • For example, if you get the measles after other childhood vaccines, does it essentially

  • wipe them out?

  • Right now, we just don't know, though there are doctors trying to develop tests that can

  • figure out what protections you've lost.

  • Because of these and other unanswered questions about measles infections, the best bet is

  • to protect everyone from getting measles to begin with!

  • Seriously, get vaccinated.

  • When enough people get vaccinated for infectious diseases like measles, it protects everyone,

  • not just those who get the shot.

  • Herd immunity ensures there isn't a large enough susceptible population to continue

  • the spread.

  • And that protects people who can't be vaccinated and other vulnerable individuals, like babies

  • or people with compromised immune systems.

  • But if you really need another reason to get the measles vaccine, here it is: you're

  • not just protecting yourself and others around you from the measles.

  • You're also helping to keep your immune system in good working order, so it can protect

  • you from all sorts of other illnesses.

  • Because no one wants a forgetful immune system!

  • No one wants a forgetful, well, anything, really.

  • Forgetting is no fun.

  • So if you want to be sure you remember all that science and math you learned in high

  • school and college, you might want to check out Brilliant.org.

  • You see, Brilliant offers interactive courses in math, science, engineering, and computer

  • science.

  • So whether you're looking to brush up on subjects you took years ago or learn something

  • new, they've got you covered.

  • And you can try their Daily Challenges, too.

  • There's a new question every day, so you can apply all the information you've learned

  • or re-learned from their courses.

  • Also, they're totally free.

  • And if that's not cool enough, the first two hundred people to sign up at Brilliant.org/SciShow

  • will get twenty percent off an annual Premium subscription.

  • So you can challenge your brain all year long and support SciShow in the process.

  • {♫Outro♫}

This episode of SciShow is supported by Brilliant!

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B2 中高級 美國腔

麻疹疫苗如何保护您免受其他疾病的侵害(How Measles Vaccines Protect You From Other Diseases)

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    joey joey 發佈於 2021 年 06 月 04 日
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