You cannot magnetize a human, or just about any object that is not ferromagnetic. Ferromagnetism basically refers to the mechanism by which certain materials can become magnetic.
Human tissue is not ferromagnetic, and so you could not make a person permanently magnetic by the use of magnets.
Certain substances, like iron, copper, sodium etc., can become magnetized in the presence of a magnetic field, and remain magnetized even when that field is gone, but the amount of these materials in the human body is miniscule, so there is no chance of this happening.
One should be very cautious with claims that the Covid vaccine can make a person "magnetic", or do anything else other than what it was designed to do. There is no evidence for this claim, and no physically consistent mechanism for how such a thing can happen.
Even if vaccines did contain magnetic materials, there certainly would never be enough to "make a person magnetic". There is less than a milliliter ($\lt 0.3$ milligrams I think) of material that is injected via the syringe, some of it, it is alleged by those who push this idea, is magnetic. But still this is nowhere near enough to create an even hardly detectable magnetic field. Think about the fact that on average, an adult human already has approximately $3-4$ grams (not milligrams, actual grams) of iron in their body. This on its own is $10,000$ times more than if the entire volume of the vaccine was a magnetic substance.
If you held a key near your liver (high in iron) would it stick? How about patients who literally are injected with iron (supplements)? Do they become magnetic? It is obviously ridiculous to claim that a vaccine could render a human magnetic, and those who make such unscientific claims maybe have other motives or are just terribly misinformed.