Listen, Never mind that:
A.) The Smallpox vaccine never contained mercury
B.) All vaccines that used thimerosal as a preservative use it in such small concentrations (0.001% (1 part in 100,000) to 0.01% (1 part in 10,000) that it can’t cause harm to a human,
and
C.) Vaccines that do not contain thimerosal as a preservative are also available for adolescents and adults, and many vaccines (including the COVID vaccine) no longer contain thimerosal.
For the Record, do you know what has about the same amount of mercury as a typical thimerosal-preserved vaccine? This can of Tuna. (Actually, I just noticed this is a 5oz can, it contains about 42mcg of mercury, a typical vaccine has about the same as a 3-oz can, 25mcg)

Let’s Put all that aside. Because you want to know what sucks WAY worse than ingesting Mercury?
I’ve used this one before, but let’s do it one more time.
Chemical compounds are not their constituent elements, and two compounds containing the same element are not the same.
This is elemental chlorine gas:

It will blister your skin and corrode your lungs from the inside, leading to rapid, painful death. It was used as a chemical weapon in World War I and is now banned (as a weapon) by international law.
This is sodium chloride—that toxic yellow-green gas, mixed with a soft, silvery metal that explodes when exposed to water.

It’s harmless in any reasonable quantity* unless you suffer from high blood pressure, and is used in and sprinkled on foods across the world. (For those who slept through grade school science class… it’s table salt.)
This is methanol—a compound of hydrogen, oxygen, and carbon.

It’s used as a coolant in submarine engines, among other things, and if you drink it, you will go blind (or just die).
This is ethanol—the exact same chemical formula as the methanol above, except with one extra carbon atom (and two extra hydrogens attached to it). That is, take the chemical formula for methanol, add one carbon atom and associated hydrogen atoms, and you get the formula for ethanol.

You shouldn’t have too much of it, but in moderate quantities, it’s safe and tasty.
Now…
Elemental mercury is neurotoxic as a vapor but harmless in its normal, liquid form. You can even drink it (not that I recommend it) and it will simply pass right through your system without being absorbed.
Mercury chloride is incredibly dangerous, as it can be absorbed through the skin and corrodes cells on contact.
Methylmercury will build up in your system and cause heavy metal poisoning.
But ethylmercury and the related compound, thimerosal, are both purged from the system rapidly enough that they are effectively* harmless. Those are the ones used (previously) as vaccine preservatives and as disinfectants.
In fact, to go from the formula for methylmercury (the bad one) to ethylmercury (the perfectly OK one), you make the exact same shift as from methanol (strike you blind) to ethanol (serve chilled with a twist of lemon)—just add one more carbon and two hydrogen.
So go get your shots!
Vaccines are never used to treat any illness, but to prevent them.
The smallpox vaccine is hardly poisonous if it were there probably wouldn’t be people left on earth.
Since Smallpox disease is extinct ( due to vaccines) it is relatively rare for anyone to be vaccinated against smallpox. The last smallpox case was in 1977.
Mercury is much like everything else, the poison is in the dose. Anything can kill you if the dose is large enough. Large dose of mercury can kill you and so can a large dose of vitamin A. We all have been exposed to larger amounts of mercury than is in a vaccine AND the type of mercury used as a preservative in a few vaccines is inert. It means it passes right through your body and is excreted.
I suspect you do not have a lot of medical knowledge. 1. a vaccine is NEVER used to treat any illness.
2. The vaccines are not poisonous and almost none have any mercury in them at all.
3 A vaccine tells your immune system “here is an enemy, if you see it destroy it, do not let it into the cell to use the energy of the cell to replicate” IT is NOT a treatment and to be honest there haven’t been a lot of successful treatments for smallpox.
4. if vaccines were poisonous you would see people dropping like flies instead people who are vaccinated are more likely to not become ill and die.
You have, I suspect, bought a lot of nonsense.