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Why Are There Dangerous Ingredients In Vaccines? - Video học tiếng Anh
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Why Are There Dangerous Ingredients In Vaccines?
Why Are There Dangerous Ingredients In Vaccines?
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Sous-titres (39)
0:01
Vaccines save more than 9 million lives each year, even though they contain ingredients
0:05
that can be pretty dangerous.
0:07
But that’s precisely the point: those nasty ingredients are the only reason that vaccines
0:11
work at all.
0:12
On their own, our bodies are already pretty good at fighting off illness.
0:15
When an unfamiliar pathogen invades our body, patrolling immune cells engulf a few of these
0:19
foes to gather intel.
0:21
The cells then churn out a chemical alarm, transmitting the enemy’s information along
0:25
the chain of command and triggering the production of specially-targeted antibodies and assassin
0:29
cells to fend off the rest of the invaders.
0:31
After the battle, some of these specialized troops stick around so that if the pathogen
0:35
returns, they can help mount a quicker response.
0:37
However, some pathogens are so powerful that they can overwhelm the immune system before
0:41
it’s able to mount a defense.
0:43
Vaccination lets us stage a practice version of this battle in advance of the real one,
0:47
so that the immune system can develop and stockpile weapons specifically targeted at
0:51
the enemy.
0:52
That does require introducing a bit of the enemy into our bodies, but it’s an enemy
0:56
that we’ve already disarmed, either by killing it, breeding a super-weak strain, or dismembering
1:00
it to get at recognizable - but not dangerous - parts.
1:04
Enter formaldehyde.
1:05
It’s a critical ingredient in some common vaccines, like those for tetanus and influenza,
1:10
because it alters the structure of those pathogens just enough to render them harmless.
1:14
This reactivity also makes formaldehyde dangerous to us in large doses, but vaccines contain
1:19
only a tiny fraction of the formaldehyde we consume and naturally produce on a daily basis.
1:25
In fact, the biggest risk with formaldehyde is that it can leave pathogens so crippled
1:28
that they won’t trigger the proper immune response.
1:31
So some vaccines contain substances called "adjuvants,” which put the immune system
1:35
on higher alert.
1:36
Aluminum, for example, causes a minor irritation at the injection site, summoning immune cells
1:40
to the scene so they’ll encounter the weakened enemy.
1:43
And although too much aluminum can be toxic, our bodies are super-efficient at eliminating
1:47
it, keeping levels low even after lots of shots.
1:50
So while boatloads of aluminum, buckets of formaldehyde, and an up-close meet-and-greet
1:54
with a full-strength pathogen are all definitely bad ideas, a controlled concoction from a
1:59
doctor is designed to be just nasty enough to keep us safe.
2:03
There’s always a chance of an adverse reaction to a vaccine’s ingredients, but the much
2:07
scarier scenario would be to let polio, measles, and other deadly diseases call
2:45
the shots.
