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