Why Are There Dangerous Ingredients In Vaccines?

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.