How do you convince people the Covid vaccine is safe?

My aunt has a sixteen year old son, so he's old enough for the vax. Problem is, he has rapid heart beat sometimes, and she read that the vaccine causes heart problems in young men and doesn't want him getting it. And now he's kinda nervous to get it too. How can I convince both of them that the shot is harmless, and won't kill him?

How do you convince people the Covid vaccine is safe?
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